text: Title: Deprecate the `"default"` colorscale name and `list_all_colorscale_names()`
  Body: The only reason we still need `list_all_colorscale_names()` is because we decided to add an extra `"default"` named color-scale to the list of available continuous color-scales. Not sure why this was done but to avoid breaking someone else's workflow, let's deprecate these first and completely drop support for it later on.