Expose Connection<I>

[connec]

• 366e0dc chore: don't deny warnings in source

  It's considered an anti-pattern to deny warnings in the source itself.
  It's better to configure this in the environment, which we already do
  for CI with -D warnings.

• ce50e47 feat!: return Connection from Endpoint::connect_*

  This is a small step towards removing the ConnectionPool. The
  ConnectionPool is used for a number of things, one of which is
  enabling the Endpoint APIs that operate exclusively on SocketAddrs,
  rather than connection handles.

  This commit exposes the Connection<I> type, and updates the
  Endpoint::new, Endpoint::connect_to, and Endpoint::connect_to_any
  methods to return Connection<I> rather than SocketAddr. For now, the
  only public method on Connection<I> is remote_address, which callers
  can then use with the existing (unchanged) SocketAddr-based Endpoint
  APIs. Future commits will introduce additional Connection methods to
  replace these SocketAddr-based APIs.

  BREAKING CHANGE: Endpoint::new, Endpoint::connect_to, and
  Endpoint::connect_to_any now use Connection<I> instead of
  SocketAddr in their return type.

• 4f0cf52 docs: expand and clarify Endpoint method documentation

  This mostly cleans up existing information about connection pooling and
  priority. Connection pooling info has been added to each method, to make
  sure the behaviour is clear in each case.

• bc0b5c7 docs: fix a broken intra-doc link

• 7d0b710 ci: upgrade wagoid/commitlint-github-action

  The new version has tighter defaults, which should prevent us from
  committing dodgy commit types like wip. The GITHUB_TOKEN has also
  been removed, since the repository is public and the action is read
  only.

• 54d1040 refactor!: replace Endpoint addr/id getters

  Rather than Endpoint having getters for addr
  (get_socket_addr_by_id) and id (get_connection_id) there are now
  only getters for Connection, either by addr
  (get_connection_by_addr) or by id (get_connection_by_id).

  For now this mostly adds indirection for callers, who can call
  Connection::id or Connection::remote_address on the result to
  achieve the same outcome as before.

  BREAKING CHANGE: Endpoint::get_connection_id and
  Endpoint::get_socket_addr_by_id have been removed.
  Endpoint::get_connection_by_addr and Endpoint::get_connection_by_id
  can be used instead to get a Connection, from which the id or
  remote_address can be retrieved.

• b3bdf3c ci: fix cargo-udeps action

  CARGO_HTTP_MULTIPLEXING has been disabled, which seems to have
  resolved our network woes, and -D warnings is removed from RUSTFLAGS
  for that job, since new nightlies may introduce additional lints that we
  wouldn't otherwise block. The SHA of the action has been pinned also, to
  ensure there are no surprise updates.

• 7110a3f test: bump timeouts in ConnectionDeduplicator tests

  The timing-based tests for this module are flaky, but since
  ConnectionDeduplicator isn't long for this world we'll live with
  bumping the timeout for now.