[libcontacts] Update section bucket index cache after deletions. Contributes to JB#46496
When a contact is deleted, we need to recalculate the section bucket index cache as that contact may have been the only contact in a given section bucket (display label group). However, since updating the section bucket index cache is an expensive operation, we should only do this once per bulk deletion, so this commit also adds support for bulk deletion operations.
Showing with 28 additions and 16 deletions