[Hide DCK devices] Hide DCK devices from settings app (saved devices page).

Set preferences of DCK devices to be invisible in saved devices page.

Test: atest: com.android.settings.bluetooth.SavedBluetoothDeviceUpdaterTest
Bug: 322285078
Change-Id: I9bd38c1866f469f3c0395b77f935f7eb143ec70c

aconfig/settings_connecteddevice_flag_declarations.aconfig

@@ -33,4 +33,11 @@ flag {
   namespace: "pixel_cross_device_control"
   description: "Order the saved bluetooth devices by most recently connected."
   bug: "306160434"
+}
+
+flag {
+  name: "enable_hide_exclusively_managed_bluetooth_device"
+  namespace: "dck_framework"
+  description: "Hide exclusively managed Bluetooth devices in BT settings menu."
+  bug: "322285078"
 }