Baking: bug in modes using Roughness bake type internally

[franMarz]

Fix baking modes using Roughness bake (includes transmission when checked the prefs option to ignore other channels) being affected by other channels (clearcot, base color, ior, specular tint and ior level and sheen roughness and tint)

Likely try Blender's EMIT baking mode? A 'linear' conversion from float to color would be needed. Check that the results are consistent while other channels are always null (0 or 1, depends on the channel type). Try different Base Color / IOR setups while performing the checks.

Add a new Prefs option to "Ignore other channels when baking Roughness", by using EMIT.