Move Android template app E2E builds to Docker

[cortinico]

Summary:

Move Android template app APK generation into a dedicated reusable workflow that runs in reactnativecommunity/react-native-android:latest.

The emulator workflow now downloads the prebuilt debug or release APK and runs Maestro directly on the Ubuntu host. Only the debug lane reconstructs the generated project as a Metro workspace. E2E retries reuse the original APK artifacts instead of rebuilding the app.

This keeps KVM-backed emulators on the host while removing Gradle and NDK provisioning from the emulator jobs. It also aligns the template app flow with the existing RNTester build/test artifact boundary.

Changelog:

[INTERNAL] [FIXED] - Build Android template E2E APKs in the Android container.

Test Plan:

• yarn prettier --check .github/workflows/build-android-templateapp.yml .github/workflows/e2e-android-templateapp.yml .github/workflows/test-all.yml — passed
• git diff --check — passed
• Parsed all three changed workflow files with the repository's yaml package — passed
• Container build and emulator E2E were not run locally because Docker is unavailable; the GitHub Actions PR run will exercise the complete workflow.

[meta-codesync]

@cortinico has imported this pull request. If you are a Meta employee, you can view this in D120393969.