Save sizes when dumping bitmaps

This change adds bitmap allocation sizes to the dumped information when
calling am dumpheap -b.

Test: check that bitmap sizes can be extracted from heap dumps
Bug: 412425223
Flag: com.android.traceur.flags.bitmaps_in_traceur
Change-Id: I34fc82b03c1003dd840824e4e0a1c14031b7abec