Setup infrastructure (multi-db support) for the new grid migration algorithm

We'll have a db for each grid option and a db for back up / restore.

TODO(pinyaoting): support back up / restore using the new infrastructure, particularly calls to GridBackupTable should use different DBs when the feature flag (NEW_GRID_MIGRATION_ALGORITHM) is on.

Bug: 144052802
Test: N/A

Change-Id: I644a3e70148bd78204a747a337446a3c038f616f
14 files changed