feat(firebase): tvOS support for firebase_analytics

[TheNoumanDev]

What does this PR do?

Adds federated firebase_analytics_tvos — Firebase Analytics for Apple TV,
built on the Firebase Apple SDK. Re-exports the firebase_analytics Dart API
and ships the native tvOS pluginClass; depends on firebase_core_tvos. Full
analytics API, no feature disables.

Package(s) touched: firebase_analytics_tvos (new)

How was it tested?

initializeApp(options:) succeeds, Analytics 12.15.0 starts, collection
enabled, and events reach the backend. Platform.operatingSystem == "tvos" and
Platform.isIOS == true under AOT.

• Ran the package's example/ app
• Verified on tvOS simulator (version: 26.2)
• Verified on a physical Apple TV (Apple TV 4K 3rd gen / tvOS 26.2)
• dart analyze is clean for the package

Versioning & changelog

• version: set to 0.0.1 (new package)
• Matching ## 0.0.1 entry at the top of CHANGELOG.md
• No behaviour change (new package)
• Semver 0.x: initial 0.0.1

Checklist

• Only firebase_analytics_tvos files are touched
• No secrets, absolute local paths, or TODO/debug left
• README.md documents tvOS behaviour (no feature limitations; version-alignment note)
• Sibling-package constraint noted below

Notes for reviewers

• Version alignment (affects all Firebase _tvos leaf packages): the native Pigeon matches firebase_analytics 12.4.3 and firebase_core_platform_interface 7.1.0 train (firebase_core 4.11.x). Mixing firebase_core_tvos with a different firebase_core whose FirebaseOptions list differs can crash in CoreFirebaseOptions.fromList at launch (Dart options: init).
• Depends on firebase_core_tvos (publish first).

[TheNoumanDev]

@MAUstaoglu @DenisovAV — this adds firebase_analytics_tvos following the same pattern as the Firebase batch in #3. Verified on a physical Apple TV 4K (tvOS 26.2): Firebase initializes, and analytics events reach the backend. Depends on firebase_core_tvos. Would appreciate a review whenever you have time — thanks!