Rebase "feat: replace x-editable with HTMX for inline editing" + other minors

[ElLorans]

Rebasing #2847 was not straightforward for me, so I am trying here before working on the original branch

[ElLorans]

Test pass, example works. I would move this rebase and updates to #2909, then merge to master. We can work from there to unlock either #2892 (which looks done to me except for x editable not working) or #2444.
Finally, we can debate wether dropping XEditableWidget should happen in a minor or major release.

EDIT: not ready yet.
Errors are not rendered. E.g.: if the user submits a non unique field on a unique constrained column, only a console error is registered.