Ajax error ajax.$form.ajaxSubmit() is not a function

Problem/Motivation

Different Drupal forms throw an ajax.$form.ajaxSubmit error on submit.

This has affected users at image upload, Block editing within Layout Builder sections, and ajax submissions for webforms. It is blocking development of various site items.

Steps to reproduce

Adding any elements to a form also gives the same error.

Steps:

1. Install & enable the webform module.
2. Add a new test form.
3. Click the "+ Add element" button.
4. Pick any element type, and fill in the form to create a new element.
5. Click the "Save" button.

Proposed resolution

Fix the bug with ajax so that Drupal users can add / modify webforms, successfully upload images etc.

Remaining tasks

Test the proposed patch.
Merge it if good.

User interface changes

None

API changes

None

Data model changes

None

Release notes snippet

NA