[d3d9] Refactor D3D9ShaderValidator and enable input count validation only for The Void

[WinterSnowfall]

Fixes #4537. I had hoped the input count validation would work globally, but apparently it regresses that particular game.

There's no nicer way to handle this unfortunately, since we're dealing with entirely undocumented behavior, so I've hidden the offending validation behind a config option and enabled it only for The Void, the only known game that actually needs it.

Also part of this PR, I've refactored the code to sit in its own .cpp file (as I should have done from the start really).

[doitsujin]

What exactly does the validation in question do, what do the shaders in The Void look like that cause it to fail, and why does it break the other game?

[WinterSnowfall]

What exactly does the validation in question do, what do the shaders in The Void look like that cause it to fail, and why does it break the other game?

The validation in question fails if a PS 3.0 uses more than 10 (higher than index 9) input registers. This is (apparently) what The Void relies on to work correctly.

As to why the game on #4537 takes issue with it, no idea, as it's no longer available for purchase, but since the validation is pretty specific, I'm sure it uses a higher than 9 index in a PS 3.0 for some reason. As of now it's the only other game (with the exception of The Void of course) that we know of to do that, but in its case it doesn't expect the validation to fail.

TLDR, this entire thing is a mess even by d3d9 standards, but since in practice only The Void needs it, I think the PR isn't too far of an ask. I lost count how many config options we have specifically for Sims 2, so we might as well have a very dubious one for The Void, at least until (if ever) we get an exact idea what the intended behavior is here, if it differs based on OS versions etc.