A11y regression due to changed return behavior

Originally reported in https://github.com/IQSS/dataverse/issues/7895 and then fixed in https://github.com/IQSS/dataverse/pull/8500 and https://github.com/IQSS/dataverse/pull/12390, we changed the behavior of the return key when entering information in the create/edit metadata form.

While the original behavior (clearing metadata on pressing return) was clearly a bug, I think we should (need to?) reconsider disabling form submission via return:

The edit metadata dialog is long and if you enter a field somewhere in a middle, it can take 40+ tabs to be able to submit the form afterwards -- a simple one-click operation with the mouse. That's bad accessibility and arguably a violation of WCAG SC 2.1.1 (and at least the spirit of 2.4.1).
Moreover, implicit submission is an HTML standard, that we're now purposefully breaking.

Disabling implicit submission in CVoc fields as 12390 does still seems like the right choice to me given the problems describe by @qqmyers related to those fields, but I would like us to go back to web standards (and easy keyboard navigation/accessibility) by restoring form submission on return when the cursor is in a regular text field..

Start by reviewing the create/edit metadata form and the linked pull requests 8500 and 12390 to understand the current return-key behavior. Done means Return submits from regular text fields while remaining disabled in CVoc fields, with keyboard navigation and accessibility behavior checked against the stated WCAG concerns.