This change moves the generation of Android APKs into a template
function so it can be called multiple times with different parameters.
The two packages generated only differ by package name and APK name,
but this lays the framework for easy future changes.

Bug: angleproject:3004
Change-Id: I6c27d379bfa5f5c2912bf04cb748983787e385ac
Reviewed-on: https://chromium-review.googlesource.com/c/1361381
Commit-Queue: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>