Android Build Optimisations

[vaslabs]

This discussion is to exchange ideas and discuss on starting to optimise the Android build.

Basically, some things in the build process are over "provisioned" (for lack of a better word) , there might be excessive things packaged in the APK or things that are using CLI tools can be optimised as jvm workers (e.g. like the KSP2)

A few things that come to mind at the moment:

• Android Test apk is separate from the main APK, but it does package the main module as well. Perhaps setting the main module as a compile only module would still work and make the test APK lighter
• Android manifest merger is used as a CLI tool, and can probably be used via a classloader
• Resources are transitively resolved (see more here)
• Native dependencies are always packaged, in gradle this setting is controlled by a flag. We can also have a setting to filter out architectures in case someone targets specific devices and want to optimise their apk (although this is possible by overriding androidPackageableNativeDeps, it needs some knowledge of mill + android)

[vaslabs]

First iteration for reducing the androidTest apk

#5963

I suspect further reduction can be done with R8 (I found evidence in Gradle's resulting apk that R8 is involved) but will leave that work for a subsequent PR