[Cocoa] Adopt -[AVContentKey externalContentProtectionStatus]
<rdar://problem/118089335>
Pull request: https://github.com/WebKit/WebKit/pull/20216
Committed 270466@main (9a2768153bb2): <https://commits.webkit.org/270466@main> Reviewed commits have been landed. Closing PR #20216 and removing active labels.