Deprecate use of cluster, metacluster, and mc_name outside of remapping

[alex-l-kong]

What is the purpose of this PR?

Closes #846. It's much easier for the user to read pixel_som_cluster as opposed to cluster, pixel_meta_cluster as opposed to metacluster, and pixel_meta_cluster_rename as opposed to mc_name. We had used these as a result of standards Zak used, but these names should be reverted outside of the remapping process.

How did you implement your changes

Any function outside of metacluster_remap_gui needs to use the new standard of column naming. When the mapping is saved after a click event of New metacluster happens, the columns get renamed prior to the save.

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[alex-l-kong]

The example dataset version will be changed to main just before merging in.

[camisowers]

Same, adding the cluster_type arg is easy to follow.