Update MM.usageAS when mremap copies or moves a mapping.
Update MM.usageAS when mremap copies or moves a mapping.

PiperOrigin-RevId: 224221509
Change-Id: I7aaea74629227d682786d3e435737364921249bf

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor