This will make sure Import-Export Addons are never filtered away, but
still not expose them to the UI list.
sidenote: maybe we should mention this in the "Filter Addons" tooltip?
(the fact that Import-Export Addons are always there...)
2nd sidenote: not sure we should rename "tags" throughout the code here
as well? Or is it planned to have this support anything else than Addon
filtering? See "WorkSpace UI Tags", "Filter the UI by tags", "UI Tags",
"Use UI Tags", "Remove all tags", "Remove ui tag", "Add ui tag", "New
name for the tag", "Tag to remove"...