Stayd authored Nov 25, 2023 and Jacob Boerema committed Dec 01, 2023

Moves most of the code relating to YCoCg and Alpha Exponent into
misc.c/h, in the interest of making the rest of the codebase cleaner.
Removes the decode option from the import menu, as encoded files are
always decoded now (there used to be a menu button for doing this
after import, but with it gone there's no reason ever to not decode).
Finally, the remaining functions in color.c were only ever called once,
so these were extracted and inlined, and the empty file deleted.