Handle devices without quota, speed up lookup.

Start tracking which block devices have quota support, and gracefully
clear FLAG_USE_QUOTA when no support is present.

Also build a cached map of mounted volumes that support quota, which
halves the average quota calculation speed from 0.70ms to 0.35ms,
since we're no longer parsing procfs every time.

Test: builds, boots, common operations work
Bug: 34249218
Change-Id: Ie791df7801b67495331f3eea256c018860c9b4f6