Projected Display: Disable enterDesktop if display does not support it.

However for other methods e.g. ADB, Overview button, where the user is
explicitly trying to start freeform windows, we will not disallow it.

Bug: 384568161
Test: atest
Flag:com.android.window.flags.enable_projected_desktop_mode
Change-Id: If701e41097e561af8af892006c183ea92ff50094