Add vulkan renderer API from suijingfeng/vkQuake3

[llbraughler]

Fixes #812

[llbraughler]

The SDL build path needs cleaned up and a few other tweaks for the other 3 platforms.

[llbraughler]

I can't see why the OpenBSD process is failing. Maybe someone else can help with that.

[NuclearMonster]

re-running the bsd one

[llbraughler]

Ok this is ready for others to test. Before merging, it would be good to squash the commits down and maybe we can leave opengl2 as the default renderer until this has proven reliable on all platforms.

[NuclearMonster]

I don't believe Vulkan is at all appropriate for defaulting due to availability and stability, unless something has changed? I believe on Mac you still have to use a metal translation layer and on other platforms I've had unpredictable behavior even on modern nvidia.

[NuclearMonster]

Was some copilot or other LLM assistance used to develop this PR?

[llbraughler]

I agree it’s not ready to be the default yet. Right now it’s just helpful to get more eyes on it and let people start using it, while gl2 stays the stable baseline. Longer term, I do expect the classic GL path to get harder to maintain as vendors lean more heavily into modern APIs, so at some point in the future it might make sense to default to Vulkan.

[llbraughler]

Squashing commits

[NuclearMonster]

Was some copilot or other LLM assistance used to develop this PR?

Please answer the question.

[llbraughler]

Yes, I used Copilot for the numerous build errors that prevented compilation