[template] Automatically apply android.packagingOptions from gradle.properties

[EvanBacon]

Why

• Android build error for ffmpeg-kit-react-native config-plugins#31 (comment)
• Provide a safe interface for modifying the android.packagingOptions in the android/app/build.gradle. Users could tap withGradleProperties to statically modify the android.packagingOptions.pickFirsts value.
• One caveat to this approach is that it's strictly additive so you can't use it to remove existing values (not a use-case I've encountered yet).

Test Plan

• Not entirely sure how to test if this works since I couldn't reproduce the build errors.

Checklist

• Documentation is up to date to reflect these changes (eg: https://docs.expo.dev and README.md).
• This diff will work correctly for expo build (eg: updated @expo/xdl).
• This diff will work correctly for expo prebuild & EAS Build (eg: updated a module plugin).

[hirbod]

I like this approach. Way better than my current regexp attempts.

[Kudo]

i've tried with the example in gradle.properties
android.packagingOptions.excludes = **/x86/libjsc.so,**/x86_64/libjsc.so,**/arm64-v8a/libhermes-inspector.so

and verify with unzip -l app/build/outputs/apk/debug/app-debug.apk | grep libjsc.so

it's even better if we could trim() the spaces. i once added a space after the , and doubt why it didn't work 😅