[AE] Add flag for AE support on Connected Displays

This is migrating the flag from the windowing_sdk namespace to lse_desktop_experience namespace as requested by the LSE team. Previous flag was added in ag/30966987

Bug: 372200182
Change-Id: Ie6d8c0554064fe99e4ec00ec7432c52ccf7bc1a5
Test: Manual
Flag: com.android.window.flags.enable_activity_embedding_support_for_connected_displays