[JENKINS-76249] Fix form submission when a dropdown changes and the back end response is slow

[jtnord]

calling renderOnDemand can cause the DOM to be manipulated aynchronously due to function calls going to the Jenkins server (e.g. stapler/bound/xxx/render). When this occurs if there is a subsequent change to the dropdown selection before this completes, when the HTML is finally obtained from Jenkins it is inserted into the DOM, but it is inserted as if it is still the selected option (ie it is not disable for the form).

renderOnDemand takes a callback function that will be called when the DOM manipulation is complete, however the updateDropDownList did not pass any function.

We now pass a function that manipulates the just added HTML if the selected item is in fact no longer selected.

Fixes #16833

Testing done

• Commented out the fix

  jenkins/war/src/main/webapp/scripts/hudson-behavior.js

  Lines 1719 to 1721 in 03eaf02

  	// our form div has changed (but the index is stable) so go and re-get the new domtree
  	var subForm = buildSubForms(e)[idx];
  	updateDropDownFormRowVisibility(subForm, false);

• Ran mvn test -Dtest=SshSlavesPluginTest#newAgent in a loop.

Observed that the test failed ~ 1 time in 10 and that the newly added console log (**** renderOnDemandCallback, selection no longer valid, form submission would have been corrupted) always appeared when the test would fail (and very rarely appeared otherwise)

• Reintroduced the fix
• Ran mvn test -Dtest=SshSlavesPluginTest#newAgent again.

Observed I still see the newly introduced console log ~ 1 time in 10m but the test did not fail in > 800 runs.

Screenshots (UI changes only)

Before

After

Proposed changelog entries

• Submitting a form would in rare cases, lead to an error (Got type array but no lister class found for type...)

Proposed changelog category

/label

Proposed upgrade guidelines

N/A

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Desired reviewers

@mention

Before the changes are marked as ready-for-merge:

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[jtnord]

for testing these 3 lines where commented out to show the previous console line was printed and the test failed ~ 1:10
Then re introduced and the test passed 100 times in a row

[timja]

Thanks!

[timja]

/label ready-for-merge

---

This PR is now ready for merge, after ~24 hours, we will merge it if there's no negative feedback.

Thanks!

[A1exKH]

LGTM.