rpc: Extend GetInfo RPC

[natalypeyioti]

This PR extends GetInfo RPC endpoint with the following info:
lnd identity pubkey, node alias, block height, block hash, synced to chain

This is an example response of the getinfo cli command with the current changes:

{
    "version":  "0.2.0-alpha commit=v0.2.0-94-g1f8dd8a-dirty",
    "lnd_version":  "0.16.2-beta",
    "network":  "signet",
    "lnd_identity_pubkey":  "031498adfc0ddd11d07b78f53230efe0986bea4278932749b95d18ccba42f0c6cf",
    "node_alias":  "031498adfc0ddd11d07b",
    "block_height":  148284,
    "block_hash":  "0000001b5aa637a8ca512471f11b4da1b1086a9e4519d953db2dd07e8c4062e4",
    "synced_to_chain":  true
}

TODO:

• universe federation
• universe stats

fixes #311

[ben2077]

May i take this？

[dstadulis]

May i take this？

go for it, @ben2077

[dstadulis]

@ben2077 if you'd like the updated feature in v0.3-alpha, If you can deliver before end of next week, it can be included in the RC tagging.

[ben2077]

@ben2077 if you'd like the updated feature in v0.3-alpha, If you can deliver before end of next week, it can be included in the RC tagging.

i will get it done.

[ben2077]

#554

[guggero]

Replaced by #554.