Add TelephonyManager test hidden API for testing

Test: atest
Bug: 172507765

Change-Id: I30a5b695770509dc803ab5623c75e653d40f4d11
Merged-In: I30a5b695770509dc803ab5623c75e653d40f4d11
(cherry picked from commit 53cfc4a8944c491934973d47f8c4503a5644b8ed)
diff --git a/telephony/java/android/telephony/TelephonyManager.java b/telephony/java/android/telephony/TelephonyManager.java
index 27aadd5..9243467 100644
--- a/telephony/java/android/telephony/TelephonyManager.java
+++ b/telephony/java/android/telephony/TelephonyManager.java
@@ -13783,6 +13783,15 @@
     }
 
     /**
+     * Setup sITelephony for testing.
+     * @hide
+     */
+    @VisibleForTesting
+    public static void setupITelephonyForTest(ITelephony telephony) {
+        sITelephony = telephony;
+    }
+
+    /**
      * Whether device can connect to 5G network when two SIMs are active.
      * @hide
      * TODO b/153669716: remove or make system API.