Android: Convert DirectoryInitialization to Kotlin

Add screen crop feature

For some reason, NativeLibrary.kt calling Log for the alert message text
makes Dolphin die with a JNI error. Supposedly the jstring passed to the
logging function is invalid. I don't understand why, because the dialog
that we show right afterwards is able to read the string just fine. The
error happens even if I pass the string directly to Log without
prepending any extra text.

There's no real downside to having the logging in C++ instead of Kotlin,
so let's move it to C++ to avoid the JNI error.

Android: Convert GameFileCacheManager to Kotlin

GCAdapter: Automatically start and stop thread

This keeps the logic encapsulated inside GCAdapter.cpp so callers don't
have to think about it.