System UI: Add config boolean to enable screen capture on desktop

This change introduces the config config_enableDesktopScreenCapture that
handles enabling the feature on desktop only. If the config is true,
clicking the screen recording tile should be a NOP.

Bug: 412722968
Test: atest ScreenRecordTileTest
Flag: com.android.systemui.desktop_screen_capture
Change-Id: Ic3c212e16cd037fa54a9af3294f0f54319e29bdd