[video_player_avfoundation] macOS platform view support

[FirentisTFW]

[DRAFT]
This PR contains changes from #8237. Once that PR is merged (and video_player package is published with platform view support on iOS and Android), this PR will be rebased and adjusted. For now it will hang as a draft.

This PR will add platform view support to video_player package for macOS.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/packages repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or this PR is exempt from CHANGELOG changes.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

[cbenhagen]

@FirentisTFW now that #8237 has been merged, what's missing to add macOS support?

[FirentisTFW]

@cbenhagen We wanted to fully release iOS and Android implementations first to have less potential pain points.

However, these were also not fully released yet. #8810 is adding the support to the app-facing package. I still haven't published it though, since it seems that there are some issues when rendering Android's SurfaceView (which is used by video_player_android) in Flutter. There's an issue for that: #164899. I was going to wait a little bit more for the Android team's input there before I try to work around it again. Only then I wanted to publish the app-facing PR and then follow up with the macOS support.