[JENKINS-71909]: Revert https://github.com/jenkinsci/active-choices-p…

[kinow]

…lugin/pull/79

The merge request mentions JENKINS-71365 (prototype.JS is removed from Jenkins core) but reverting this should not impact that.

What we are doing is removing the async calls and promises, and instead using the synchronous code again. This is so that Active Choices parameters are rendering in order as they were before.

Whilst rendering them asynchronously seemed like a good idea to provide a more responsive UI, in reality we oversaw an important aspect: users write their scripts relying on the order parameters are loaded.

Users wrote their code using document.getElementId, for instance, which worked previously as users would put the parameter doing that after the parameter from which the ID was being used.

There were several issues rendered, so this is not likely to be added back again any time soon. In order to have a more smart reactivity, we would need places to hook user callback code (like Vue or React do), but provided by Jenkins UI, or in a way that could take some time to create in the plug-in without breaking things, and that works well.

Testing done

Submitter checklist

• [x] Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• [x] Ensure that the pull request title represents the desired changelog entry
• [x] Please describe what you did
• [x] Link to relevant issues in GitHub or Jira
• [x] Link to relevant pull requests, esp. upstream and downstream changes
• [x] Ensure you have provided tests - that demonstrates feature works or fixes the issue