refactor reportPasswordChanged

* Refactor method to call saveSettingsLocked
  once for each userId

Manual testing steps
* Set up device with an admin eg. Device Owner
* Add PIN
* Change PIN

Bug: 71536124
Test: atest com.android.server.devicepolicy.DevicePolicyManagerTest
      Manual Testing
Change-Id: Idf9b30498117db649a7326653e48e38c55cc3b70