Add initial compile tests

[GaryQian]

In discussion for https://github.com/flutter/flutter/issues/84868, We are seeing differences when running flutter build depending on if the contents of android/.gradle directory is populated or not. This is because gradle will download dependencies and generate the .gradle file on first run of the app.

This PR splits the inital compile time into initial and full, where initial implies building from a fully untouched never-before-compiled project, while full implies building after just running flutter clean.

This change adds about ~30s of build time to the hello_world_android__compile test task