Frameworks: Annotate trivial @GuardedBy in packages

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)$").

Derived by errorprone.

Bug: 73000847
Test: m
Change-Id: Id14322b0a6206152cd2933c968e0a6f470fcee09

packages/ExternalStorageProvider/src/com/android/externalstorage/ExternalStorageProvider.java

@@ -145,6 +145,7 @@ public class ExternalStorageProvider extends FileSystemProvider {
         }
     }
 
+    @GuardedBy("mRootsLock")
     private void updateVolumesLocked() {
         mRoots.clear();