GS: Pre-round/truncate STQ values based on hardware tests

[refractionpcsx2]

Description of Changes

Pre-rounds and truncates STQ float values for textures on sprites.

Rationale behind Changes

Extracted as safe code to use from #6553 so we can at least get the manhunt fixes in for the lighting.
We did some tests on hardware, and we found the truncating of float values gets pretty crazy depending on the difference between values. What is done in this PR seems to work pretty well for a bunch of games, however hardware mode won't feel all the fixes, I believe due to the difference in how GPU's handle texture coordinates.

Suggested Testing Steps

Test any games including the ones listed below, make sure nothing looks busted in software and hardware.

All the following results are on Software mode

Ben 10:
Master:

PR:

Armored Core 2:
Master:

PR:

Beyond Good & Evil:
Master:

PR:

G-Force: (kind of subjective but certainly not bad, matches some other lines on the scene)
Master:

PR:

Manhunt:
Master:

PR:

Shinobido - Way of the Ninja (this isn't right either, tbh, but neither is master, and the PS2 is janky as well)
Master:

PR:

PS2 for reference:

Persona 3:
Master:

PR:

Persona 3 again:
Master:

PR:

[stenzek]

Probably should do some performance testing, this per-vertex loop looks quite heavy. Vectorizing it could be.. tricky.

[refractionpcsx2]

For the moment I've limited this to sprites and flat draws only to try and avoid performance problems.

We do plan to move this to the vertex shaders + Software JIT directly where we should be able to do it with more performance, at that point the ghost rider shadow will work correctly.