The gradle build scripts can be configured to output different
application IDs for different build types, so we need to examine the
built .apk to figure out the name of the package and activity.

Re-landing this change, updated to only get information from the .apk
if it exists.

Since the tools create an AndroidApk instance early, even before we've
actually built an .apk, we have to create a new instance after building,
so we can start the right app/activity.

Fixes #8327.