Flag to guard clearing collision state on pairing conclusion

Change-Id: Ibda88392bde3d9e094858b4e50940113ab7db8fd
Test: mma packages/modules/Bluetooth
Bug: 327208896
Bug: 315241296

flags/pairing.aconfig

+package: "com.android.bluetooth.flags"
+container: "com.android.btservices"
+
+flag {
+    name: "clear_collision_state_on_pairing_complete"
+    namespace: "bluetooth"
+    description: "Clear authentication collision state on pairing conclusion"
+    bug: "327208896"
+}