Add feature flag to public API for IMS service.

This commit adds a feature flag to define public API for IMS service.
These flags allow use of specific APIs as public API.

Bug: 359721349
Test: build pass
Flag: com.android.internal.telephony.flags.support_sms_over_ims_apis
Change-Id: Id5c72a0550859a3609dd47efade3958f1f21f193
diff --git a/flags/ims.aconfig b/flags/ims.aconfig
index d2401fe..4426933 100644
--- a/flags/ims.aconfig
+++ b/flags/ims.aconfig
@@ -137,3 +137,11 @@
         purpose: PURPOSE_BUGFIX
     }
 }
+
+# OWNER=meghapatil TARGET=25Q2
+flag {
+    name: "support_sms_over_ims_apis"
+    namespace: "telephony"
+    description: "Used to expose SMS related hidden APIs for SMS over IMS to public API."
+    bug:"359721349"
+}