Screen capture: Guard settings button in toolbar behind feature flag

The settings button in the pre-capture UI toolbar controls screen
recording settings. Guard the visibility of the button behind a new
feature flag for screen recording on large screen devices.

Bug: 430991124
Test: Manually verify UI
Flag: com.android.systemui.large_screen_recording
Change-Id: Ie4cea4b12d9398d88e055e322dd31a9716dfe35c