Implement Google in app update api

[AjeshRPai]

Implement the Google in app update api in the app.

### Tasks
- [ ] Check for app updates
- [ ] If a flexible update is available, then show an update available option. On clicking update, trigger flexible update 
- [ ] If an immediate update option is available, trigger immediate update

[peril-wordpress-mobile]

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🚫	Please add a type label to this issue. e.g. '[Type] Enhancement'

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[dangermattic]

Thanks for reporting! 👍

[jkmassel]

Closing — this has been fully implemented. The codebase has a complete Google In-App Update API integration:

• Dependency: com.google.android.play:app-update:2.1.0 in the version catalog
• Core classes: InAppUpdateManagerImpl, IInAppUpdateManager interface, InAppUpdateListener, plus a no-op variant
• Both update types: Flexible (background) and Immediate (blocking) updates are supported
• Feature-flagged: Controlled via InAppUpdatesFeatureConfig remote config (in_app_updates)
• Configurable: Blocking version and flexible update interval are remotely configurable
• Analytics: Tracks shown/accepted/dismissed/completed events
• Integration: Wired into WPMainActivity with proper lifecycle handling
• Tests: Unit tests exist for both the manager and analytics tracker

All three task list items (check for updates, flexible update, immediate update) are covered by the existing implementation.