Cleanup JNI of java.lang.*

[tobrun]

On the JNI side we have multiple files responsible for the definitions of java.lang.* classes:

• https://github.com/mapbox/mapbox-gl-native/blob/release-boba/platform/android/src/java_types.hpp
• https://github.com/mapbox/mapbox-gl-native/blob/release-boba/platform/android/src/java/lang.hpp

cc @ivovandongen