Changes UserSystemPackageInstaller log TAG to use its own class name.

This class issues a lot of "PKG is allowlisted but not present" logs
on boot, which makes it harder to watch other log messages on
UserManagerService.

Test: adb logcat UserManagerService *:s
Bug: 226643927

Change-Id: I8dbd32fd06b133b7e7136d11133a2fac121d1b9b

services/core/java/com/android/server/pm/UserSystemPackageInstaller.java

@@ -95,7 +95,7 @@ import java.util.Set;
  * </code></pre>
  */
 class UserSystemPackageInstaller {
-    private static final String TAG = "UserManagerService";
+    private static final String TAG = UserSystemPackageInstaller.class.getSimpleName();
 
     private static final boolean DEBUG = false;