QCamera2/HAL3: Cache metadata in batch mode

In batch mode, only one metadata is sent from back-end per
batch. It can be *copied* as multiple metadata for rest of
the frames in the batch instead of parsing the same
metadata buffer again

BUG=28312446
CRs-Fixed: 1038197

Change-Id: I5be580e69b8f14e8a381111a787c38081fb04f71
2 files changed