Feature Request

I confirm:

• that I haven't found another request for this feature.
• that I have checked whether there are updates for my system available that
  contain this feature already.

Description

Currently, while PROTON_USE_WINED3D disables DXVK for every other D3D version, it does not for D3D8. That is separately controlled by PROTON_DXVK_D3D8.

Justification

The fact that PROTON_USE_WINED3D disables every other DXVK backend, and the name of the var, suggests that it's meant to be a catch-all.

Besides, the D3D8 backend depends on the D3D9 one, which is disabled by the aforementioned setting, so leaving it enabled when the D3D9 backend is disabled will just make games crash (it caused me some confusion until I found out about the separate toggle).

D3D10 and 11 have separate toggles as well, but both are auto-disabled with the "catch-all" toggle.