Replace the `required` boolean column on cookie_categories with a `kind`
enum (NORMAL, NECESSARY, UNCATEGORISED). The Necessary category remains
undeletable and always-on for consent; the new Uncategorised category is
also undeletable but users can opt out of it.
When a category is deleted, its cookies are merged into the Uncategorised
category (lazy-created for legacy banners that don't have one yet).
Signed-off-by: Émile Ré <emile@getprobo.com>
7cd8c516b9