With the NDK installed locally, gradle plugin 3.6.0 seems to enforce
a specific older NDK version, and will fail building if you don't have
it installed with:
```
No version of NDK matched the requested version 20.0.5594570.
Versions available locally: 21.0.6113669
```
Upstream issue: https://github.com/gradle/gradle/issues/12440
- update gradle plugins versions
- add formatting rules for AndroidManifest and gradle build files
- cleanup java_godot_lib_jni
Note: logic was mostly moved around and no new logic/functionality was added.
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').
