[video_player_avfoundation] Add video track selection support

[nateshmbhat]

Summary

AVFoundation breakout PR for #10688.

• Implements getVideoTracks() and selectVideoTrack() methods using AVFoundation
• Video track selection requires iOS 15+ / macOS 12+ for HLS streams
• Adds comprehensive Swift and Dart unit tests

Dependency Chain

This PR is third in a series of breakout PRs:

1. video_player_platform_interface ([video_player_platform_interface] Add video track selection support #11474) - pending
2. video_player_android ([video_player_android] Add video track selection support #11475) - pending
3. video_player_avfoundation (this PR)
4. video_player + video_player_web (pending - original PR [video_player] : Add video track selection support for Android and iOS #10688 updated)

Note: This PR depends on video_player_platform_interface 6.7.0 being published first.

Test Plan

• Swift unit tests for video track retrieval and selection in VideoPlayerTests.swift
• Dart unit tests for AVFoundationVideoPlayer overrides

[gemini-code-assist]

Code Review

This pull request introduces video track selection functionality to the AVFoundation video player plugin, specifically for HLS streams on iOS 15+ and macOS 12+. It adds new native methods to retrieve available video tracks and to select a preferred bitrate. The Dart side integrates these native methods, converting native data structures into VideoTrack objects and providing an API for track selection. New tests have been added to cover this functionality, and the plugin version has been updated to 2.10.0. Feedback suggests improving error handling in getVideoTracks for failed asset variant loading and populating assetTracks for non-HLS videos to ensure consistent track information and avoid dead code on the Dart side.

[gemini-code-assist]

The implementation of getVideoTracks does not handle the case where loading the asset variants fails. If status is AVKeyValueStatusFailed, the error parameter of statusOfValueForKey:error: will be populated, but it is currently ignored, and the method proceeds to return an empty result. It would be better to check for failure and return a FlutterError to provide better diagnostics to the Dart side.

[gemini-code-assist]

The assetTracks parameter is explicitly set to nil here, which means that for non-HLS videos (or HLS videos where variants aren't used), no video track information will be returned. However, the Pigeon definition and the Dart implementation in AVFoundationVideoPlayer.dart (lines 250-271) include logic to handle assetTracks. This results in dead code on the Dart side. Consider populating assetTracks using [urlAsset tracksWithMediaType:AVMediaTypeVideo] to provide consistent track information for all video types, even if they don't support quality selection.

[stuartmorgan-g]

This PR requires #11474 to land and be published.

[gemini-code-assist]

Code Review

This pull request implements video track selection for the video_player_avfoundation package. It introduces the VideoTrack class and adds getVideoTracks, selectVideoTrack, and isVideoTrackSupportAvailable methods to the VideoPlayerPlatform interface. The iOS and macOS implementation utilizes the AVAssetVariant API for HLS streams on supported OS versions and provides basic support for regular video assets. Comprehensive tests have been added across the platform interface, the Dart implementation, and the native Swift code. I have no feedback to provide.

[nateshmbhat]

@stuartmorgan-g pr unblocked as platform_interface update is published