Use internal SubManagerService

Use internal subscriptionmanager service to gain access to all active subscriptions regardless its associated profile, then filter by caller profile.
And gate user handle filtering activity with a new feature flag so
that it can be advanced independent from enterprise feature. It should
cause no behavior change because currently no client can assign a SIM to
a profile.

Bug: 296076674
Test: data browsing + voice call + sending sms
Change-Id: Ie851f2c6ed12a70fa67797baa35c7ce62bedbeb7
diff --git a/flags/subscription.aconfig b/flags/subscription.aconfig
index 0521cb9..dece11a 100644
--- a/flags/subscription.aconfig
+++ b/flags/subscription.aconfig
@@ -5,4 +5,11 @@
   namespace: "telephony"
   description: "To support separation between personal and work from TelephonyManager and SubscriptionManager API perspective."
   bug: "296076674"
+}
+
+flag {
+  name: "enforce_subscription_user_filter"
+  namespace: "telephony"
+  description: "Enabled flag means subscriptions enforce filtering result base on calling user handle. It marks the telephony completion of user filtering."
+  bug: "296076674"
 }
\ No newline at end of file