Inline editing: prevent editing read-only values

As a follow up task, let's also make sure the read-only values are not editable with inline editing that's currently being added: https://github.com/nextcloud/tables/issues/364. A few column types already merged as of yesterday: https://github.com/nextcloud/tables/pull/1719

_Originally posted by @enjeck in https://github.com/nextcloud/tables/pull/1958#pullrequestreview-3090379155_
            