Clean up JNI local handles code

JNI Local handles can only be created by JavaThread (there's an assert in make_local) but the fields are added to Thread.
Move the fields to JavaThread and adding JavaThread* argument.
Also, the global freelist isn't very useful now that global JNI handles don't use JNIHandleBlock, so the locking that claims incorrectly to block for safepoint is removed.
Lastly, there's at least 3 places that duplicate pushing a new JNIHandleBlock to the thread for temporarily adding JNI local handles. These have been moved to common code with a JNIHandleMark object, moved from jvmci code.