The previously used file sharing api was restricted after Android N causing the engine to crash whenever used on devices running Android N or higher.
(cherry picked from commit b04c9a71f4)
This was done by refactoring directory and file access handling for the Android platform so that any general filesystem access type go through the Android layer.
This allows us to validate whether the access is unrestricted, or whether it falls under scoped storage and thus act appropriately.
The application module `app` serves double duties of providing the prebuilt Godot binaries ('android_debug.apk', 'android_release.apk') and the Godot custom build template ('android_source.zip').