Clean up libwebrtc Xcode project. This removes some missing (unused) files/folders, and manually fixes issues found by `tidy-Xcode-project-file` from Bug 188754.
<rdar://problem/116386161>
This is step 1 of 2. The second step is to run `tidy-Xcode-project-file` to do the automated clean up.
Pull request: https://github.com/WebKit/WebKit/pull/18537
Committed 268771@main (34ebac9a5f68): <https://commits.webkit.org/268771@main> Reviewed commits have been landed. Closing PR #18537 and removing active labels.
Re-opening for pull request https://github.com/WebKit/WebKit/pull/18550
Committed 268773@main (36c3a8590f2b): <https://commits.webkit.org/268773@main> Reviewed commits have been landed. Closing PR #18550 and removing active labels.