[video_player] Adds audio track metadata fetching and audio track selection feature

[nateshmbhat]

Description

This PR adds comprehensive audio track retrieval and selection support to the video_player package, enabling developers to access detailed information about available audio tracks and switch between them during playback.

Changes Made

Core Features

• Added VideoAudioTrack model with comprehensive metadata fields: id, label, language, isSelected, bitrate, sampleRate, channelCount, codec
• Added getAudioTracks() method to retrieve all available audio tracks with real metadata
• Added selectAudioTrack() method to switch between audio tracks during playback
• Updated VideoPlayerController to expose audio track functionality

Platform Implementations

• Android:
  • Real metadata extraction using ExoPlayer's getCurrentTracks() API
  • Robust track selection using TrackSelectionOverride with proper error handling
  • Support for multiple audio formats (AAC, AC3, EAC3, MP3, etc.)
• iOS:
  • Metadata extraction from AVFoundation using AVAssetTrack for regular videos
  • HLS stream support using AVMediaSelectionGroup for adaptive streams
  • Proper track selection for both asset tracks and media selection options

Technical Infrastructure

• Updated Pigeon interfaces for both Android and iOS with new data structures:
  • AudioTrackMessage, ExoPlayerAudioTrackData, AssetAudioTrackData, MediaSelectionAudioTrackData, NativeAudioTrackData
• Enhanced platform interface with new methods and data classes
• Has native unit tests for both Android and iOS platforms
• Created demo screen showcasing audio track functionality with interactive UI

Demo Features

• Interactive video player with audio track selection
• Real-time metadata display (bitrate, sample rate, channels, codec)
• Support for multiple video sources including HLS streams
• Visual indicators for currently selected tracks

Related Issues

#59437 - Add audio track metadata support to video_player

Testing

• Added native unit tests for both Android and iOS
• Tested with various video formats and HLS streams
• Verified backward compatibility with existing functionality
• Demo screen widget for manual testing and validation

Breaking Changes

None - all changes are additive and backward compatible.

Pre-Review 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].
• I signed the [CLA].
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [video_player]
• 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 I have commented below to indicate which [version change exemption] this PR falls under[^1].
• I updated CHANGELOG.md to add a description of the change, [following repository CHANGELOG style], or I have commented below to indicate which [CHANGELOG exemption] this PR falls under[^1].
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which [test exemption] this PR falls under[^1].
• All existing and new tests are passing.

[gemini-code-assist]

Code Review

This pull request introduces a valuable feature for fetching and selecting audio tracks in the video_player package. The changes are comprehensive, touching the platform interface, Android (ExoPlayer) and iOS (AVFoundation) implementations, and adding a new demo screen.

My review has identified several critical and high-severity issues that should be addressed:

• The new native unit tests for both Android and iOS appear to be broken due to type mismatches and incorrect method calls, and will not compile in their current state.
• The Dart implementation code for both Android and iOS contains unsafe null assertions on data coming from the native side, which could lead to runtime crashes.
• The Android implementation has been updated to use a milestone version of Gradle, which is not recommended for production packages.
• The new audio track selection feature has not been implemented for the web platform, which will lead to UnimplementedError on web.
• There is a minor issue in the new example app where context is used after an await without checking if the widget is still mounted.

Addressing these points will significantly improve the robustness and completeness of this new feature.

[nateshmbhat]

I updated native andorid tests and ran the tests and verified that all native android tests are passing.

[nateshmbhat]

@stuartmorgan-g @ash2moon can you please comment on this PR and lemme know if there are any concerns ?

[nateshmbhat]

any update on this PR ?

[stuartmorgan-g]

From triage: ping @tarrinneal @ash2moon @LongCatIsLooong @hellohuanlin for review

@nateshmbhat Apologies for the delay; things have been unusually busy recently. A couple of high-level notes while you are waiting for full reviews:

• The video_player_web changes can all be reverted; it looks like you probably ran the auto-formatter in the package without running pub get, so applied the wrong formatter version.
• It appears that one of the new tests is crashing on macOS.
• If this feature isn't going to be implemented on all platforms, it needs to have a support query so clients know if they can call it.