Deprecate the worker_thread factory overload

Marks the CreatePeerConnectionFactory overload that takes a worker
thread as [[deprecated]] and migrates the remaining in-tree callers to
the overload without worker_thread.

The overload keeps forwarding the caller's worker thread, so
applications that supply a thread that is distinct from the network
thread still get the runtime diagnostics in addition to the compile time
warning.

See https://groups.google.com/g/discuss-webrtc/c/Fs_Hd5XNJh0

Bug: webrtc:558821261
Change-Id: I3677d4cf659337f072ecb676c33d683b05a71add
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/502960
Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48817}