Flutter Android build: Automate the upload of debug symbols

[orkun1675]

Use case

See https://github.com/orgs/codemagic-ci-cd/discussions/2900#discussioncomment-11818663.

TLDR: When Flutter apps use obfucation the debug symbols are not included in the .aab due to a long standing issue. This requires developers to manually generate and upload a zip file every time they want to release a build (or risk not getting readable logs/Crashylytics).

This is a very prevalent complaint:

• [Android] Document fix for warning "native debug symbols are missing in appbundle" when uploading app to playconsole flutter/flutter#98773 has 21 upvotes.
• https://stackoverflow.com/questions/62568757/playstore-error-app-bundle-contains-native-code-and-youve-not-uploaded-debug/79104473#79104473 has hundreds of engagements
• https://www.youtube.com/watch?v=3ieKwhmQg7I&t=405s&ab_channel=iRekhaTechSolutions has thousands of views

Idea

First a script can be used to generate the debug symbols zip:

rm -rf build/app/intermediates/stripped_native_libs/release/out/lib/.crashlytics \
&& cd build/app/intermediates/stripped_native_libs/release/out/lib/ && zip -r ../../../../../outputs/bundle/release/symbols.zip . && cd - \
&& mkdir -p build/$1/android_build/ \
&& cp build/app/outputs/bundle/release/symbols.zip build/$1/android_build/ \
&& echo "Upload the following debug symbols to Play Console: 'build/$1/android_build/symbols.zip'" \
|| echo "Build for Android failed!"

Then we can utilize the Google Play Developer API upload endpoint to upload this zip to the Play store. Note that we will need to specify deobfuscationFileType=nativeCode when calling this endpoint.