[Cocoa] Transition Legacy Fairplay CDM off AVStreamSession
<rdar://problem/107202864>
Pull request: https://github.com/WebKit/WebKit/pull/12378
Committed 262647@main (2ef8f77a149f): <https://commits.webkit.org/262647@main> Reviewed commits have been landed. Closing PR #12378 and removing active labels.