Move focus for windows in freeform mode

This CL updates the logic for moving the focus to the adjacent task/activity/window to include freeform windowing mode.

Bug: 373880470
Change-Id: Id9e60ec25583476dcf2b632a1084f4aea025ed39
Test: atest ActivityEmbeddingFocusTests
Test: atest TaskFragmentTest#testMoveFocusToAdjacentWindow
Test: Run commands: `adb shell input keyevent KEYCODE_DPAD_XXX` while running 2-pane Settings in full screen and freeform windowing modes.
Flag: EXEMPT bugfix