MNT: migrate IDL colormaps to cmyt

[neutrinoceros]

Bug report

Bug summary
As seen recently with #3911, it'd be worth migrating more code from yt to cmyt (namely the yt/visualization/color_maps.py module and _colormap_data) to leverage cmyt's fast release cycle and avoid having to make much heavier yt releases.

I think I can handle this migration before yt 4.1 so I'll triage this ticket as such.

[neutrinoceros]

I still think this is a good idea (probably), but I don't want it to weight on the release so let's take it out of the milestone