Summary: public
Kill `RCTPerfStats` and introduce the new `RCTPerfMonitor`, including memory
usage, JSC heap size, number of RN views in screen, FPS (both on UI and JS threads)
and more to come.
It removes all the previous traces that were previous spread across the bridge
and the dev menu and moves everything to be more contained, so the whole thing
can be safely striped in production.
Reviewed By: nicklockwood
Differential Revision: D2575158
fb-gh-sync-id: 6a6d0c4422adbddeeefddd32ec3409a7095ff2a9