[Cocoa] Adopt AVContentKeySession compatibility mode APIs
<rdar://problem/97347572>
Pull request: https://github.com/WebKit/WebKit/pull/5052
Committed 255287@main (ef443ccb8927): <https://commits.webkit.org/255287@main> Reviewed commits have been landed. Closing PR #5052 and removing active labels.
Reverted by https://github.com/WebKit/WebKit/pull/5155
Committed 255295@main (ea3d0e681f4b): <https://commits.webkit.org/255295@main> Reviewed commits have been landed. Closing PR #5155 and removing active labels.
Re-opening for pull request https://github.com/WebKit/WebKit/pull/6139
Committed 256351@main (5299b9b5bf85): <https://commits.webkit.org/256351@main> Reviewed commits have been landed. Closing PR #6139 and removing active labels.
Re-opening for pull request https://github.com/WebKit/WebKit/pull/6172
Committed 256356@main (02eddf0c9b88): <https://commits.webkit.org/256356@main> Reviewed commits have been landed. Closing PR #6172 and removing active labels.