[Feature]: Add option to force FSR3 instead of 4

[Billli11]

Please confirm the following before submitting

• I haven't found another open request for this feature.
• I have checked whether a system update already provides this feature.

Description

With game start shipping with AMD FidelityFX 2.1.0 and later.

Game will use FSR4 on RDNA3 automatically without any ENV set. (tested on screamer and Far Far West.)

As long as vkd3d-proton is built with fp8 emulation enabled.

edit: workaround

VKD3D_DISABLE_EXTENSIONS=VK_KHR_cooperative_matrix

Do any thing else use WMMA? xess?

Justification

No response

Risks

No response

References

No response

[loathingKernel]

this has been fixed and will be in the next release