build: clean up pc/BUILD.gn dependencies

Also let gn_check_autofix ignore the libjingle_peerconnection_api target.

done using
  tools_webrtc/gn_check_autofix.py -r pc/BUILD.gn
followed by
  tools_webrtc/gn_check_autofix.py -C out/Default/
and picking the non-controversial changes.

Manually adding the test:test_main target to unit test binaries was required.

Bug: webrtc:467294026
Change-Id: Id3a4c3dc22297789b17283692d88af26af400e94
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/432621
Reviewed-by: Jeremy Leconte <jleconte@google.com>
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46447}