Print peak regions allocated metric at GC perf dump

Maximum (of all GC iterations) peak regions allocated
is printed during GC perf dump which reflects space
pressure on allocator.

Bug: b/69633530
Test: Any bench with -XX:DumpGCPerformanceOnShutdown cmdline flag
Change-Id: I0e2960825c5637955e9dfb677e5ed65ed852ba93
3 files changed