Frameworks: Annotate trivial @GuardedBy in services/core

Add @GuardedBy for simple functions that require locks and have a name in
one of the frameworks naming styles for locks ("^.*(Locked|LPw|LPr|L[a-zA-Z]|UL|AL|NL)$").

Changelist for statsd.

Derived by errorprone.

Bug: 73000847
Test: m
Change-Id: I02981b3f65102640609c8ca85c765250b0e2e3ad

services/core/java/com/android/server/stats/StatsCompanionService.java

@@ -1179,6 +1179,7 @@ public class StatsCompanionService extends IStatsCompanionService.Stub {
         }
     }
 
+    @GuardedBy("StatsCompanionService.sStatsdLock")
     private void forgetEverythingLocked() {
         sStatsd = null;
         mContext.unregisterReceiver(mAppUpdateReceiver);