Vulkan: LightmapGI Use Color property not implemented (unlike BakedLightmap in 3.x)

[Calinou]

See also #50570.

Godot version

4.0.dev (8747f25)

System information

Fedora 34, GeForce GTX 1080 (NVIDIA 465.31)

Issue description

LightmapGI doesn't have a use_color property, unlike BakedLightmap in 3.x. This can be used to decrease the file size of the generated lightmap, which can be important when exporting to mobile and web platforms. The difference between grayscale and colored lightmaps is sometimes only barely noticeable when baking indirect lighting only, so it may not be much of a visual tradeoff.

See godotengine/godot-proposals#2142.

Steps to reproduce

Look for a use_color property in the master branch's LightmapGI node.

Minimal reproduction project

N/A