Merge AVPictureInPictureController support into VideoFullscreenInterfaceAVKit
<rdar://problem/98579829>
Pull request: https://github.com/WebKit/WebKit/pull/4911
Pull request: https://github.com/WebKit/WebKit/pull/7617
Committed 258013@main (3ac8f1b746a6): <https://commits.webkit.org/258013@main> Reviewed commits have been landed. Closing PR #7617 and removing active labels.