Entity::insert_many() auto-chunking for large inserts

[nickb937]

There is a limitation when using Entity::insert_many with PostgreSQL when inserting a large number of rows, resulting in a panic!:

[2023-12-11T15:53:31Z INFO  sqlx::query] summary="SELECT col1, col2, ..., colN FROM table rows_affected=16854 rows_returned=16854 elapsed=487.267501ms
thread 'main' panicked at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-postgres-0.7.3/src/message/parse.rs:31:13:
assertion failed: self.param_types.len() <= (u16::MAX as usize)
stack backtrace:
   0: rust_begin_unwind
             at /rustc/79e9716c980570bfd1f666e3b16ac583f0168962/library/std/src/panicking.rs:597:5
   1: core::panicking::panic_fmt
             at /rustc/79e9716c980570bfd1f666e3b16ac583f0168962/library/core/src/panicking.rs:72:14
   2: core::panicking::panic
             at /rustc/79e9716c980570bfd1f666e3b16ac583f0168962/library/core/src/panicking.rs:127:5
   3: <sqlx_postgres::message::parse::Parse as sqlx_core::io::encode::Encode>::encode_with::{{closure}}
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-postgres-0.7.3/src/message/parse.rs:31:13
   4: <alloc::vec::Vec<u8> as sqlx_postgres::io::buf_mut::PgBufMutExt>::put_length_prefixed
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-postgres-0.7.3/src/io/buf_mut.rs:25:9
   5: <sqlx_postgres::message::parse::Parse as sqlx_core::io::encode::Encode>::encode_with
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-postgres-0.7.3/src/message/parse.rs:25:9
   6: sqlx_core::net::socket::buffered::BufferedSocket<S>::write_with
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-core-0.7.3/src/net/socket/buffered.rs:85:9
   7: sqlx_core::net::socket::buffered::BufferedSocket<S>::write
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-core-0.7.3/src/net/socket/buffered.rs:78:9
   8: sqlx_postgres::connection::executor::prepare::{{closure}}
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-postgres-0.7.3/src/connection/executor.rs:50:5
   9: sqlx_postgres::connection::executor::<impl sqlx_postgres::connection::PgConnection>::get_or_prepare::{{closure}}
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-postgres-0.7.3/src/connection/executor.rs:177:66
  10: sqlx_postgres::connection::executor::<impl sqlx_postgres::connection::PgConnection>::run::{{closure}}
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-postgres-0.7.3/src/connection/executor.rs:214:18
  11: sqlx_postgres::connection::executor::<impl sqlx_core::executor::Executor for &mut sqlx_postgres::connection::PgConnection>::fetch_many::{{closure}}::{{closure}}
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-postgres-0.7.3/src/connection/executor.rs:377:71
  12: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/79e9716c980570bfd1f666e3b16ac583f0168962/library/core/src/future/future.rs:125:9
  13: <futures_util::future::future::fuse::Fuse<Fut> as core::future::future::Future>::poll
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/futures-util-0.3.29/src/future/future/fuse.rs:84:26
  14: futures_util::future::future::FutureExt::poll_unpin
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/futures-util-0.3.29/src/future/future/mod.rs:558:9
  15: <sqlx_core::ext::async_stream::TryAsyncStream<T> as futures_core::stream::Stream>::poll_next
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-core-0.7.3/src/ext/async_stream.rs:106:15
  16: <core::pin::Pin<P> as futures_core::stream::Stream>::poll_next
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/futures-core-0.3.29/src/stream.rs:120:9
  17: <S as futures_core::stream::TryStream>::try_poll_next
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/futures-core-0.3.29/src/stream.rs:196:9
  18: <futures_util::stream::try_stream::try_filter_map::TryFilterMap<St,Fut,F> as futures_core::stream::Stream>::poll_next
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/futures-util-0.3.29/src/stream/try_stream/try_filter_map.rs:76:47
  19: <core::pin::Pin<P> as futures_core::stream::Stream>::poll_next
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/futures-core-0.3.29/src/stream.rs:120:9
  20: <S as futures_core::stream::TryStream>::try_poll_next
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/futures-core-0.3.29/src/stream.rs:196:9
  21: <futures_util::stream::try_stream::try_collect::TryCollect<St,C> as core::future::future::Future>::poll
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/futures-util-0.3.29/src/stream/try_stream/try_collect.rs:46:26
  22: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/79e9716c980570bfd1f666e3b16ac583f0168962/library/core/src/future/future.rs:125:9
  23: sqlx_core::query::Query<DB,A>::fetch_all::{{closure}}
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sqlx-core-0.7.3/src/query.rs:204:34
  24: <sea_orm::database::transaction::DatabaseTransaction as sea_orm::database::connection::ConnectionTrait>::query_all::{{closure}}::{{closure}}
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sea-orm-0.12.7/src/database/transaction.rs:455:26
  25: <sea_orm::database::transaction::DatabaseTransaction as sea_orm::database::connection::ConnectionTrait>::query_all::{{closure}}
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sea-orm-0.12.7/src/database/transaction.rs:430:5
  26: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/79e9716c980570bfd1f666e3b16ac583f0168962/library/core/src/future/future.rs:125:9
  27: sea_orm::executor::insert::exec_insert::{{closure}}
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/sea-orm-0.12.7/src/executor/insert.rs:228:52
  28: migrate::main::{{closure}}
             at ./migrate/src/main.rs:46:78
  29: tokio::runtime::park::CachedParkThread::block_on::{{closure}}
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/park.rs:282:63
  30: tokio::runtime::coop::with_budget
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/coop.rs:107:5
  31: tokio::runtime::coop::budget
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/coop.rs:73:5
  32: tokio::runtime::park::CachedParkThread::block_on
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/park.rs:282:31
  33: tokio::runtime::context::blocking::BlockingRegionGuard::block_on
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/context/blocking.rs:66:9
  34: tokio::runtime::scheduler::multi_thread::MultiThread::block_on::{{closure}}
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/scheduler/multi_thread/mod.rs:87:13
  35: tokio::runtime::context::runtime::enter_runtime
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/context/runtime.rs:65:16
  36: tokio::runtime::scheduler::multi_thread::MultiThread::block_on
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/scheduler/multi_thread/mod.rs:86:9
  37: tokio::runtime::runtime::Runtime::block_on
             at /home/nickb/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.34.0/src/runtime/runtime.rs:350:45
  38: migrate::main
             at ./migrate/src/main.rs:50:5
  39: core::ops::function::FnOnce::call_once
             at /rustc/79e9716c980570bfd1f666e3b16ac583f0168962/library/core/src/ops/function.rs:250:5

The offending panic! is defined here:

https://github.com/launchbadge/sqlx/blob/main/sqlx-postgres/src/message/parse.rs#L30-L31

I feel that it may be the responsibility of the TryInsert::exec functions to transparently chunk the data for insert, or perhaps the TryInsert::add function to fail early if the underlying driver cannot support more than self.columns.len() * self.values.len() in a prepared statement.