[2/n] Stop connected displays from being auto-enabled

Currently displays are auto-enabled on connection, skipping the (old) dialog entirely. This small change now makes it so that displays will need input from the dialog to be enabled and launch into desktop mode or mirroring.

Bug: 413620089
Test: ExternalDisplayPolicyTest
Flag: com.android.window.flags.enable_updated_display_connection_dialog
Change-Id: I3229021336bd188fe4b13c0b77e8f4419a2b8f51