[dxvk] Optimize for the d3d9 Strict float emulation path

[Blisto91]

This is more or less a port of the same feature request for the amd open source Linux driver GPUOpen-Drivers/AMDVLK#346 which has been implemented already.
While Windows is not officially a targeted platform for dxvk a few games does ship it, like some of the Valve Source 1 games. Nvidias RTX Remix also utilizes a dxvk fork (though i don't know if it still relevant there) and it isn't uncommon for Windows users to try and use dxvk for various older games.

The d3d9 Strict float emulation path in dxvk (see links below for technical description) is not enabled by default for all drivers, even though it is more correct for d3d9 floating point rules, because it has a performance penalty compared to the default True.
Amdvlk open on Linux have code to optimize for this and so will use Strict out of the box without any performance penalty and with more games functioning out of the box without visual issues.

Amd Windows currently doesn't do this and so will either have a performance penalty when dxvk is used in any games where dxvk sets Strict by default or risk of visual issues in any games where such builtin configs doesn't exist yet. An example illustrating the performance dip can be seen below.

Risen

d3d9.floatEmulation = True

d3d9.floatEmulation = Strict

See original dxvk PR doitsujin/dxvk#2294
See also the various comments below the amdvlk open request GPUOpen-Drivers/AMDVLK#346 (comment)
And Linux radv MR https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13436

[Blisto91]

Would it be possible to get some feedback on this? If there isn't interest in working on it then i can just close the request again.

Best regards.