Add flag for the PackageMonitor

Add flag to control the feature, register receiver only if really
request to support package restart query in the PackageMonitor.

Bug: 300309050
Test: build pass
Change-Id: I042456e5f475f1d4b709ad38dbe977953ab2cdfe
diff --git a/core/java/android/content/pm/flags.aconfig b/core/java/android/content/pm/flags.aconfig
index 205f1e9..45591d7 100644
--- a/core/java/android/content/pm/flags.aconfig
+++ b/core/java/android/content/pm/flags.aconfig
@@ -248,3 +248,11 @@
     bug: "316916801"
     is_fixed_read_only: true
 }
+
+flag {
+    name: "package_restart_query_disabled_by_default"
+    namespace: "package_manager_service"
+    description: "Feature flag to register broadcast receiver only support package restart query."
+    bug: "300309050"
+    is_fixed_read_only: true
+}