Add more memory usage stats

Added support for teasing apart different parts of the dalvik heap.

Note this adds more public api and we should talk to hackbod before going into master with this.

(cherry picked from commit 73407daf3f6110e933d8614605b21586c4c5fde2)

Change-Id: If4431f50e67e18bcc42e00694c97805477bd6815