Lower-overhead version of LockGuard.

Instead of building up a giant set of all locks inside the system
server, there are only a handful that we're interested in watching:
specifically those below the ActivityManagerService lock.

This change adds a index-based variant of lock registering and
checking, which has much lower overhead that doesn't bring a device
to its knees.  It's disabled by default, but can be enabled on local
development builds.

Currently uses the boostPriorityForLockedSection() hook in AMS to
check for lock inversions when enabled.

Test: builds, boots, no AMS lock inversions detected
Bug: 35410906
Change-Id: I473d634d23c08538029412a1254bf4f92b96fb84