Replace ObjectSet with LargeObjectBitmap.

Speeds up large object marking since large objects no longer required
a lock. Changed the GCs to use the heap bitmap for marking objects
which aren't in the fast path. This eliminates the need for a
MarkLargeObject function.

Maps before (10 GC iterations):
Mean partial time: 180ms
Mean sticky time: 151ms

Maps after:
Mean partial time: 161ms
Mean sticky time: 101ms

Note: the GC durations are long due to recent ergonomic changes and
because the fast bulk free hasn't yet been enabled. Over 50% of the
GC time is spent in RosAllocSpace::FreeList.

Bug: 13571028

Change-Id: Id8f94718aeaa13052672ccbae1e8edf77d653f62
22 files changed