Add e2e tests for multi-value textfield widget in page data form

We're getting fatals from the backend on adding a third item, so this is catching an actual regression.

Will dig into it tomorrow

Got to the bottom of this, the code we added for the media library to keep track of form state cache didn't work if the triggering element in an ajax callback had limit validation errors.

Bumping to critical bug because I marked 🐛 Page Data Form + Options as Buttons error on AJAX submits Active as a duplicate
Assigning to @bnjmnm to review

🤪🤯 Wow wow wow @ ClientDataToEntityConverter::setEntityFields(), but given the detailed (and essential!) comments left by @larowlan on there, I feel zero need to step through all that again to verify it. This looks ready to me.

Unfortunately the widget-multivalue.cy.js e2e test failed with

      cy:command ✘  assert	expected **<input#edit-field-xbt-unlimited-text-0-value--5Ex2yiBamp4.rt-reset.rt-TextFieldInput.js-text-full.text-full.form-text>** to have value **item five**, but the value was **item one**

Retesting… 🤞

I'm running into the same test failure locally , which is an existing test that also deals with the multi-value textfield widget. It failing on the portion of the test where the items in the multivalue field are reordered. The dragging of the lower item to the top no longer seems to register.

This still works manually, though, so hopefully it's just a matter of tweaking widget-multivalue.cy.js a bit. Unassigning myself for now.

This still works manually, though, so hopefully it's just a matter of tweaking widget-multivalue.cy.js a bit. Unassigning myself for now.

I had a thought about this while I was on leave - I think the issue is the realDnd code we have is confused by the fact the field is in a fixed height scrollable pane. When the test was written we had a small number of fields but as we've expanded things it has now grown. I'll see if making the weight of this field lighter so that is shows in the viewport without scrolling makes a difference.