Change card cache mod-union table to use bitmaps

Previously used card sets, using bitmaps saves memory and slightly
increases performance.

Added mod union table test.

Performance EvaluateAndApplyChanges (minimal changes):

Before (card cache image mu table):
UpdateAndMarkImageModUnionTable: Avg: 524.320us
ImageModUnionClearCards: Avg: 54.580us
Native PSS: ~67500kB

After (card cache image mu table):
UpdateAndMarkImageModUnionTable: Avg: 515.600us
ImageModUnionClearCards: Avg: 53.780us
Native PSS: ~66014kB

Native PSS was higher before since the mod_union_table->SetCards()
which happens pre zygote fork was allocating a large amount of
std::nodes.

Bug: 11859910

Change-Id: I956b7e51d5572feec1393ffa618b7b7d8c147b28