Add flag for migration of MTE policy to DPE

First part of the work to migrate MTE policy from ActiveAdmin to
DevicePolicyEngine.

Test: N/A - adding a flag.
Bug: 376213673
Flag: EXEMPT only adding a new flag
Change-Id: Iea4f58cf65eb172fbd5222cf148f7d5f5be0bd0c
diff --git a/core/java/android/app/admin/flags/flags.aconfig b/core/java/android/app/admin/flags/flags.aconfig
index fd58377..3aaca25 100644
--- a/core/java/android/app/admin/flags/flags.aconfig
+++ b/core/java/android/app/admin/flags/flags.aconfig
@@ -341,3 +341,11 @@
     purpose: PURPOSE_BUGFIX
   }
 }
+
+flag {
+    name: "set_mte_policy_coexistence"
+    is_exported: true
+    namespace: "enterprise"
+    description: "Enables coexistence support for Setting MTE policy."
+    bug: "376213673"
+}