Block forms are submitted prematurely

Thanks @michaellander, the points mentioned in the issue summary seem legit to me and while there should be a better way provided by core, which doesn't need this to be cirumvented, I think the patch from #6 is the right way at the moment.

Still this needs to be postponed on ✨ Add #element_submit and #limit_element_submit just like #element_validate and #limit_validation_errors Needs work , I think it would be nice to have maintainer feedback here? For super experienced maintainers like @Berdir I think it should be one look to tell what's wrong or right (but of course his time is limited and expensive)

So should we POSTPONE this for now? Or wait for feedback?

Patch #6 does not apply.

silvi.addweb → made their first commit to this issue’s fork.

Raised MR for the same.