Remove gap between screenIds when restoring from single display device

- In RestoreDbTask.sanitizeDb, add extra step to fill all screenIds gaps so that no empty pages are left in between
  e.g. [0, 3, 4, 6, 7] -> [0, 1, 2, 3, 4]

Fix: 201085524
Test: RestoreDbTaskTest
Change-Id: If0b577bf789347cc490ada0b22f2cd39ee1a33bb
4 files changed