Desktop screenshots: Connect pre-capture UI to large-screen content

Also reorganizes large-screen-specific view models and interactors to
the appropriate package.

Bug: 420715358
Test: atest PreCaptureViewModelTest
Test: atest ScreenshotInteractorTest
Flag: com.android.systemui.desktop_screen_capture
Change-Id: I0447ea3dffde10c8bbb5e66728d1552c2d8ace4e