Update to SDL3 and target Android 15.

Currently game selection (the "LOVE Loader") equivalent is currently broken, but it will be addressed in future cleanup.

gradle.properties

@@ -14,6 +14,5 @@ app.version_name=12.0
 # No need to modify anything past this line!
 android.enableJetifier=false
 android.useAndroidX=true
-android.defaults.buildfeatures.buildconfig=true
 android.nonTransitiveRClass=true
 android.nonFinalResIds=true