warn when phx-update="stream" is missing

[SteffenDE]

This logs an error to the JS console when debug mode is enabled to warn users when they forgot to add phx-update="stream" to the direct parent of an inserted stream item.

[SteffenDE]

Note that we could also warn in LiveViewTest (I have the code lying around to do it):

warning: The stream container with id "users" is missing the phx-update="stream" attribute.

    <div id="users"><div id="users-1" data-count="0">
       chris
       <button phx-click="delete" phx-value-id="users-1">delete</button><button phx-click="update" phx-value-id="users-1">update</button><button phx-click="move-to-first" phx-value-id="users-1">make first</button><button phx-click="move-to-last" phx-value-id="users-1">make last</button><button phx-click="move" phx-value-id="users-1" phx-value-name="moved" phx-value-at="1">
         move
       </button><button phx-click="[[&quot;hide&quot;,{&quot;to&quot;:&quot;#users-1&quot;}]]">JS Hide</button></div><div id="users-2" data-count="0">
       callan
       <button phx-click="delete" phx-value-id="users-2">delete</button><button phx-click="update" phx-value-id="users-2">update</button><button phx-click="move-to-first" phx-value-id="users-2">make first</button><button phx-click="move-to-last" phx-value-id="users-2">make last</button><button phx-click="move" phx-value-id="users-2" phx-value-name="moved" phx-value-at="1">
         move
       </button><button phx-click="[[&quot;hide&quot;,{&quot;to&quot;:&quot;#users-2&quot;}]]">JS Hide</button></div></div>


LiveView needs this attribute to properly patch items on the client.

  (elixir 1.19.0-dev) lib/enum.ex:992: anonymous fn/3 in Enum.each/2
  (elixir 1.19.0-dev) lib/enum.ex:4511: anonymous fn/3 in Enum.each/2
  (elixir 1.19.0-dev) lib/enum.ex:4964: Enumerable.List.reduce/3
  (elixir 1.19.0-dev) lib/enum.ex:4511: Enum.each/2
  (phoenix_live_view 1.0.2) lib/phoenix_live_view/test/dom.ex:356: Phoenix.LiveViewTest.DOM.patch_id/4
  (phoenix_live_view 1.0.2) lib/phoenix_live_view/test/client_proxy.ex:656: Phoenix.LiveViewTest.ClientProxy.patch_view/4
  (phoenix_live_view 1.0.2) lib/phoenix_live_view/test/client_proxy.ex:156: Phoenix.LiveViewTest.ClientProxy.init/1
  (stdlib 6.1.2) gen_server.erl:2229: :gen_server.init_it/2
  (stdlib 6.1.2) gen_server.erl:2184: :gen_server.init_it/6
  (stdlib 6.1.2) proc_lib.erl:329: :proc_lib.init_p_do_apply/3

but the stacktrace is not very helpful.