Allow to show pinned taskbar when Launcher is visible

This CL allows freeform-first devices to lock the taskbar in a pinned
state when Launcher is visible.

Bug: 361419732
Flag: com.android.window.flags.enter_desktop_by_default_on_freeform_displays
Test: DisplayControllerTest
Test: manual

Change-Id: Ic0d2740e33fee19c676d88aa2bcf370eb64366e8