Respect formnovalidate attribute on a button with an AJAX callback

Problem/Motivation

When using client side validation with AJAX forms. The attribute formnovalidate is not respected.

The library is supporting this: https://jqueryvalidation.org/reference/#link-skipping-validation-on-submit

Steps to reproduce

Enable validation on AJAX in the settings.
Create a Drupal form with a button with the attribute formnovalidate. The validation is then canceled.
If you enable AJAX on this form, or a AJAX callback on the button, the attribute is ignored due the code in cv.jquery.validate.js

Proposed resolution

Add an extra statement that is checking if the attribute is set.

Remaining tasks

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User interface changes

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API changes

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Data model changes

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