Windows: fix a crash between two Windows example clients running on same machine and fighting for the camera.

With this change both sides stay stable and video continues. Also tested with 2+ cameras on single device. Both clients grab their own camera and stay connected even if I remove a camera in the middle of a call.

- Manage local video capturer lifetime in Conductor: hold a ref to CapturerTrackSource and release it after DeletePeerConnection(), replacing the async PostTask destruction path in CapturerTrackSource and avoiding the Windows embedded camera crash.
- Tolerate Windows camera drivers that switch delivery threads by removing the single-thread DCHECK at the start of CaptureInputPin::Receive.
- Stop the remote renderer when a remote track is removed to avoid rendering a stale frame after the video track ends.
- Scope: examples/peerconnection client and Windows capture; no changes on other platforms.

Changes: 
Bug: webrtc:457610948
Change-Id: Ifcc848661dabafb7ef5696df1fdb360219ddd31d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/422881
Auto-Submit: Gregory Bolshakov <gubidonius@gmail.com>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Per Kjellander <perkj@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46141}