Add interactive view above status bar.

Adds an invisible view layered above status bar to forward input through
the existing handleCaptionThroughStatusBar logic. This reduces our
reliance on a global input monitor and also fixes an issue where desktop
mode could be invoked by dragging down in handle coordinates even while
notification shade is active.

Bug: 349135068
Bug: 341997116
Test: manual
Flag: com.android.window.flags.enable_additional_windows_above_status_bar
Change-Id: I94120c64c7f359661fca632df0251989cd93fa07