This PR refactors what is remaining of HTML table API to divs.
It is mainly about the body and aggregate footer.
Because a `position: sticky` creates a stacking context, and because a
div wrapping other divs prevents those children divs from being sticky,
it has been found that removing the wrapping container of both header
and footer allows us to have all z-index in the same stacking context
and create the right experience.
Though the fine-tuning of z-index will be done in another PR.
There are many fixes left that will be addressed very soon in subsequent
PRs.
This PR focuses on bringing a functional table both with and without
RecordGroups. (Check Task views for that)
