Fix ordering for event processing.

The `processSafetyEvent` method relies on the state available prior
to changing it (e.g. for logging resolving actions).

Also slight cleanup to use SafetySourceKey directly in more places.

Bug: 296215753
Test: atest SafetyCenterHostSideTestCases
Relnote: Fix some logging ordering issue for Security & Privacy screen
Change-Id: I12dc836118c503b1b1cfa78c7d24f3555697cb97