[video_player] Platform view support

[FirentisTFW]

TODO:

• add documentation to readme

This PR adds support for platform views as on optional way of displaying a video (as an alternative to Flutter's Texture widget). Texture-based approach is still the default setting when creating a new player.

Platform interface was updated in #8453
Platform implementations were added in these PRs:

• iOS: [video_player_avfoundation] iOS platform view support #8237
• Android: [video_player_android] Platform view support #8466

Closes flutter/issues/86613.

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.

[nateshmbhat]

@FirentisTFW @tarrinneal when can this PR get merged 🙏🏻

[FirentisTFW]

@nateshmbhat Looks like there's an issue with displaying SurfaceViews in Android (see #164899). We'll have to either wait for it to get fixed, try to find a workaround for it first or maybe just release this feature for iOS for now. I'm afraid there's no clear timeline for it yet, but I'll update you once I know more about this.

[nateshmbhat]

@nateshmbhat Looks like there's an issue with displaying SurfaceViews in Android (see #164899). We'll have to either wait for it to get fixed, try to find a workaround for it first or maybe just release this feature for iOS for now. I'm afraid there's no clear timeline for it yet, but I'll update you once I know more about this.

@FirentisTFW since most of the performance issues and crashes that we're hearing are more predominant in ios, i think its worth releasing this now for just ios 🙏🏻
Please consider this 🙏🏻