buDefaultThemes (color themes) don't get appended to editor-settings object on non-prepress post types

[acketon]

This bug was found during CFA by @hirozed and I. The buDefaultThemes function here:
https://github.com/bu-ist/bu-blocks/blob/develop/src/init.php#L232
is limited to only load on post types returned in the bu_prepress_get_post_types() function. So when blocks are extended to non-prepress post types this seems to fail and the editor settings don't have the buDefaultThemes color arrays to use. Since non-prepress post types don't have a publication applied the buPublicationThemes part of the blocks also doesn't work (as expected) so you get no color themes showing up.

I think we need to remove this and try loading the buDefaultThemes everywhere.
A PR for CFA has more details written up: https://github.com/bu-ist/r2-cfa/pull/271

Here is an example of how a block ultimately loads the colors from either buDefaultThemes or buPublicationThemes: https://github.com/bu-ist/bu-blocks/blob/develop/src/blocks/pullquote/pullquote.js#L204