Make ENABLE_OPENGL and ENABLE_VULKAN toggle associated code when compiling

[emiyl]

This will enable building without OpenGL or Vulkan, which helps to build on devices without either graphic API, such as iOS.

Changes

• Only compile OpenGL and Vulkan specific files when they are enabled
• Changed a load of if/else statements for graphic APIs to some lovely switch statements instead
• #ifdef'd all the switch statements and any OpenGL and Vulkan specific functions
• Created a "RendererCore.cpp" file for functions that all the renderers use.
• MainWindow is now more resilient if the config shows an unknown graphic API value
• Fixed an issue in LatteDecompilerAnalyzer where it would check if the API isn't Metal only when Metal was enabled
• GeneralSettings2 now has an m_api_map, so that graphic API values stay consistent with wxChoice box

[emiyl]

why has this been removed? this function has a lot of opengl stuff in it 🤔

[goeiecool9999]

Because the whole file is not compiled now when OpenGL is disabled. I added an ifdef at the call site.

[emiyl]

..oh yeah

[goeiecool9999]

Just a heads up, I have moved all of the index cache stuff from RendererCore back to OpenGLRendererCore. It's only used by OpenGL. Vulkan and Metal have their own implementation

[emiyl]

Oh sweet thank you - I wasn't too sure what was needed and what wasn't for those two functions so I kinda just shoved everything over until it built lol - this looks a lot cleaner though