Introduce Telephony2gUpdater to Apply 2g User Restrictions

Listens for the following actions and ensures that 2g is enabled
or disabled based on the state of the `DISALLOW_2G` user
restriction. 2g is enabled or disabled for all active subscriptions
on the device.

* A broadcast for action `android.os.action.USER_RESTRICTIONS_CHANGED`
* A callback from `SubscriptionManager` informing us of a subscription
state change

Test: atest Telephony2gUpdaterTest
Bug: 230669497
Change-Id: I819d412bc14cb98a5874d2a42b50d4e4483b4b02
diff --git a/tests/src/com/android/TestContext.java b/tests/src/com/android/TestContext.java
index 7edbed9..7c3a842 100644
--- a/tests/src/com/android/TestContext.java
+++ b/tests/src/com/android/TestContext.java
@@ -31,6 +31,7 @@
 import android.os.Looper;
 import android.os.PersistableBundle;
 import android.os.Process;
+import android.os.UserManager;
 import android.telecom.TelecomManager;
 import android.telephony.CarrierConfigManager;
 import android.telephony.SubscriptionManager;
@@ -58,6 +59,7 @@
     @Mock TelephonyManager mMockTelephonyManager;
     @Mock SubscriptionManager mMockSubscriptionManager;
     @Mock ImsManager mMockImsManager;
+    @Mock UserManager mMockUserManager;
 
     private SparseArray<PersistableBundle> mCarrierConfigs = new SparseArray<>();
 
@@ -147,6 +149,9 @@
             case(Context.TELEPHONY_IMS_SERVICE) : {
                 return mMockImsManager;
             }
+            case(Context.USER_SERVICE) : {
+                return mMockUserManager;
+            }
         }
         return null;
     }
@@ -165,6 +170,9 @@
         if (serviceClass == SubscriptionManager.class) {
             return Context.TELEPHONY_SUBSCRIPTION_SERVICE;
         }
+        if (serviceClass == UserManager.class) {
+            return Context.USER_SERVICE;
+        }
         return null;
     }