GS: Renderer Code Cleanup

[TellowKrinkle]

Description of Changes

A bunch of semi-unrelated changes I made while working on the Metal implementation of depth feedback

• Move some enums to a header that's shared between Metal and C++. Maybe we can find a way to share it with the other shading languages too, but for now at least that's one less place to desync.
• Switched draw config dump to fmt from iostream and moved its definitions out of headers (not a huge fan of filling headers with private methods where not necessary, though I realize C++ seems to encourage this for some reason).
• Cleaned trailing whitespace from some glsl and hlsl shaders
• Removed some redundant ps selector bits
  • Not only were they redundant but the shaders were coded to make it seem like all sorts of absurd combinations were possible. What does it mean to do AFAIL_ZB_ONLY without COLOR_FEEDBACK? Might that ever happen? With the COLOR_FEEDBACK flag removed, the answer is now obvious: no, it would never have happened. The only flag that was ever actually used in multiple configurations was RGB_ONLY, so that one has been split into RGB_ONLY and RGB_ONLY_SW_Z. ZB_ONLY now implies COLOR_FEEDBACK, and FB_ONLY implies DEPTH_FEEDBACK.
• Fixed a bug in the Metal shaders where we forgot to update when we switched the dual-source blend AFAIL handling to use RGB_ONLY_DSB instead of RGB_ONLY

Rationale behind Changes

Easier to work with

Suggested Testing Steps

Make sure I didn't break depth feedback on non-Metal

Did you use AI to help find, test, or implement this issue or feature?

No

[TJnotJT]

The changes look good. The PS_*_FEEDBACK flags were redundant, so removing them makes sense. AA1 uses the depth feedback flag, but adapting it to these changes should be fairly straightforward.

[JordanTheToaster]

Breaks accurate alpha test in D3D12.

[TJnotJT]

Maybe we can find a way to share it with the other shading languages too, but for now at least that's one less place to desync.

At some point, we could add a utility function in GSShaderEnums.h to generate the #defines, which could work for both HLSL and GLSL.

Switched draw config dump to fmt from iostream and moved its definitions out of headers.

Minor nit: the string representations are now parenthesized instead of following #, so they wouldn’t parse cleanly as YAML. Probably not important unless something relies on that.

[TellowKrinkle]

Minor nit: the string representations are now parenthesized instead of following #, so they wouldn’t parse cleanly as YAML. Probably not important unless something relies on that.

Personally I think these should prioritize being human readable, and humans generally consider the enum name more important than the number. If you're worried about machine readability, I also changed the blend prints to print them as actual equations instead of a pile of enum cases.

If someone wants a machine readable version, we should just dump the hex number of the entire selector, which would require much less code to turn back into a selector. And wouldn't require a YAML parser, just a sscanf.