experimental flag to run Jenkins without YUI

[mawinter69]

The YUI library is old and no longer maintained.

Add a user experimental flag to disable YUI. The flag is disabled by default. When enabling the flag, all the YUI related js libraries and css classes are not loaded.

Following PR are required to get Jenkins to not show any errors
#9488
#9453
#7569

Some plugins that use YUI (not complete):
credentials
ldap
global-build-stats
build-monitor
categorized-view
matrix-project

Plugins that make use of makeButton (not complete)
credentials (fixed with jenkinsci/credentials-plugin#533)
openid

acceptance-test-harness

Testing done

Proposed changelog entries

Add a user experimental flag to run Jenkins without the YUI JavaScript library. Plugin authors should enable this flag and fix any issues that result from the removal of the YUI library.

Proposed upgrade guidelines

N/A

Submitter checklist

Beta Give feedback

1. The Jira issue, if it exists, is well-described.
2. The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood (see examples). Fill in the Proposed upgrade guidelines section only if there are breaking changes or changes that may require extra steps from users during upgrade.
3. There is automated testing or an explanation as to why this change has no tests.
4. New public classes, fields, and methods are annotated with @Restricted or have @since TODO Javadocs, as appropriate.
5. New deprecations are annotated with @Deprecated(since = "TODO") or @Deprecated(forRemoval = true, since = "TODO"), if applicable.
6. New or substantially changed JavaScript is not defined inline and does not call eval to ease future introduction of Content Security Policy (CSP) directives (see documentation).
7. For dependency updates, there are links to external changelogs and, if possible, full differentials.
8. For new APIs and extension points, there is a link to at least one consumer.

Desired reviewers

@mention

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

Maintainer checklist

Beta Give feedback

1. There are at least two (2) approvals for the pull request and no outstanding requests for change.
2. Conversations in the pull request are over, or it is explicit that a reviewer is not blocking the change.
3. Changelog entries in the pull request title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood.
4. Proper changelog labels are set so that the changelog can be generated automatically.
5. If the change needs additional upgrade steps from users, the upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the pull request title (see example).
6. If it would make sense to backport the change to LTS, a Jira issue must exist, be a Bug or Improvement, and be labeled as lts-candidate to be considered (see query).

[janfaracik]

Looks good to me! Thanks for compiling that list.

[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!

[daniel-beck]

Some plugins that use YUI (not complete):

Add matrix-auth and azure-ad to the list due to their use of YAHOO.lang.

[mawinter69]

I've collected all usages of YUI here:
https://docs.google.com/spreadsheets/d/1UjvtFmNmEdjMN5DUoFxJfBryA8q-E5_HwOzVKbVG9b0/edit?usp=sharing