Inject ApprovalsUtil in more places

Replace static methods taking a ReviewDb with instance methods.

Change-Id: I12d17fe122144183eeb142918a0176bc48e1705c
Inject ChangeUtil, making most methods non-static

Change-Id: I14c49cb4a0b9829d751ea96cd2d909f234654508
Merge changes I14c49cb4,I12d17fe1

* changes:
  Inject ChangeUtil, making most methods non-static
  Inject ApprovalsUtil in more places