From 127ace4d8887 Tweak upstream gn files for Firefox build in many places, the BUILD.gn files have files commented out, or disabled using if (false). These should be placed behind !build_with_mozilla so we can upstream the BUILD.gn changes.

The folling git commits have has history rewritten to correct issues we created as
we moved quickly through getting libwebrtc builds working. In a few cases, the
commit disappears in our github stack because a change could be reverted completely.

Bug 1654112 - Tweak upstream gn files for Firefox build. r=ng
Bug 1654112 - Changes to support building with external libyuv. r=ng
Bug 1766646 - (fix-f9ee0e08ec) limit create_cross_traffic deps
Bug 1766646 - (fix-15a3c3fdca) restrict deps in windows_version_unittest
Bug 1766646 - (fix-8615bf0582) restrict deps in frame_buffer_unittest
Bug 1766646 - (fix-b6f002b55f) build fixes for new usage of libyuv
Bug 1766646 - (fix-5cfcf2282a) build fixes for new usage of libyuv
Bug 1766646 - (fix-b09d87232b) fixes for new usage of libyuv and libdav1d
Bug 1766646 - (fix) breakout Call::Stats and SharedModuleThread into seperate files
Bug 1766646 - forking base_capturer_pipewire.cc before e1e05afec7d7d10bb77fd00c5bd72cf17d77120d
Bug 1790097 - (fix-2a2f3ece15) remove build DEP for upstream's third_party/libaom
Bug 1790097 - (fix-4eab9f47a5) remove build DEP for upstream's third_party/libaom

Depends on D163991

https://hg.mozilla.org/mozilla-central/rev/81d86382ee46
https://hg.mozilla.org/mozilla-central/rev/c531e8fe3687