ControllerConfigDiag: Potentially fix scaling problems on high DPI

Fixes issue 7940 hopefully.
PixelShaderCache: Don't use GetDimensions() for the sample count.

This function is bugged on Windows 7, and statically declaring the sample count is trivial anyway.
Merge pull request #1769 from Armada651/msaa-samples

PixelShaderCache: Don't use GetDimensions() for the sample count.
Merge pull request #1718 from lioncash/wxdoesitagain

ControllerConfigDiag: Potentially fix scaling problems on high DPI