VCN: Replace hidden API getCarrierConfigSubset(Context, int, String)

This is a preparation CL for moving VCN to a mainline module

Bug: 288465472
Test: atest FrameworksVcnTest && atest CtsVcnTestCases
Flag: EXEMPT pure refactoring
Change-Id: I44470a231cdcf4c0a35c54aba5b1967a0bdb2dd7
diff --git a/services/core/java/com/android/server/vcn/TelephonySubscriptionTracker.java b/services/core/java/com/android/server/vcn/TelephonySubscriptionTracker.java
index 96a25da..1e82b89 100644
--- a/services/core/java/com/android/server/vcn/TelephonySubscriptionTracker.java
+++ b/services/core/java/com/android/server/vcn/TelephonySubscriptionTracker.java
@@ -322,9 +322,16 @@
 
         if (SubscriptionManager.isValidSubscriptionId(subId)) {
             // Get only configs as needed to save memory.
-            final PersistableBundle carrierConfig =
-                    CarrierConfigManager.getCarrierConfigSubset(mContext, subId,
-                            VcnManager.VCN_RELATED_CARRIER_CONFIG_KEYS);
+            PersistableBundle carrierConfig = new PersistableBundle();
+            try {
+                carrierConfig =
+                        mCarrierConfigManager.getConfigForSubId(
+                                subId, VcnManager.VCN_RELATED_CARRIER_CONFIG_KEYS);
+
+            } catch (RuntimeException exception) {
+                Slog.w(TAG, "CarrierConfigLoader is not available.");
+            }
+
             if (mDeps.isConfigForIdentifiedCarrier(carrierConfig)) {
                 mReadySubIdsBySlotId.put(slotId, subId);