[Admin] Modal should open in place and load edit form remotely

[tvdeyen]

Final comment from #6014

So, what we would need to do is open the modal on click and display the result from the edit route. This is exactly what we do in Alchemy and this is very successful, fast (because we do not reload the table displayed under the modal, just the form), semantic and even tests work without JS enabled.

I could port this over to Solidus, but there is much more involved, because currently the admin is build to open the modal on the edit page and redisplaying the whole table. Which is painful for performance, but this is how things are implemented and fixing that will cost more time than I am willing to invest right now.