Creates test for the following things:
- Whether a combination of BackBufferCount + SwapEffect results in another buffer being added that acts as a front buffer. We used to have bugs caused by this in DXVK ages ago. - GetFrontBufferData actually copying data from the front buffer to the target surface and not from one of the back buffers. This is motivated by a DXVK bug with a modded version of Silent Hill 2 we had recently. - GetFrontBufferData produces a specific fixed alpha value depending on whether the swapchain is windowed or fullscreen. That's a TODO for now because neither Wine nor DXVK implements this and it's a bit annoying to implement this while not a single application is known to rely on this. - GetFrontBufferData is supposed to capture a screenshot of the entire monitor. So this MR adds a test to make sure that the application window is positioned correctly in the target surface after calling GetFrontBufferData. Total War Medieval 2 actually hit this issue with DXVK on its loading screen in windowed mode.
All the new tests pass on Windows 11 on the Nvidia D3D9 driver.
-- v2: d3d9: Add test for GetFrontBufferData window placement.