Color spaces for presentation

[kainino0x]

Split out from #197. See #197 (comment)
where we decided we should land other stuff eagerly before figuring this part out for WGPUSurfaceConfiguration.

[kainino0x]

Jan 4 meeting:

• Just add a color space enum and add it to WGPUSurfaceConfiguration. This is all WASM needs and it is probably enough for native too.
• CF: Complicated part is exposing surface capabilities (which pairs of color space + format are valid)
  • But less urgent
  • There will be a way to query this (probably a list of pairs like wgpu), and validation in Configure()
• KN: Initial native implementation can just only allow WGPUColorSpace_Undefined and not implement any other values (even WGPUColorSpace_sRGB)
  • CF: Why - is there a difference?
  • (discussion about whether/when compositors distinguish “sRGB” vs “display-native” on SDR displays, and some stuff about HDR)