Add flag to defer focus resume in non-focused windows.

This flag gates logic to prevent focus from being restored to a view
within a background window when a user exits touch mode, such as by
pressing an arrow key on a physical keyboard.

Bug: 438781414
Change-Id: Ib922ffe512964c23d62d58a545c3f5c05567242a
Flag: com.android.window.flags.defer_resume_focus_in_non_focused_window