Register help icon again

[NotMyFault]

The proposed change addresses a regression from the ionicon support PR: https://github.com/jenkinsci/jenkins/pull/6186/files#diff-f58b5cf9ae51828d19d0b7d299430741ba3ee9d4679d6213da61aaea0b3d1540L520-L521

A bunch of plugins actually rely on it, and it used to be a registered icon before.

I've chosen the help outline ionicon, I guess that fits the best, instead of reverting to material icons.

Proposed changelog entries

• Restore missing help icon (regression in 2.335).

Proposed upgrade guidelines

N/A

Submitter checklist

• (If applicable) Jira issue is well described
• Changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developer, depending on the change). Examples
  • Fill-in the Proposed changelog entries section only if there are breaking changes or other changes which may require extra steps from users during the upgrade
• Appropriate autotests or explanation to why this change has no tests
• New public classes, fields, and methods are annotated with @Restricted or have @since TODO Javadoc, as appropriate.
• For dependency updates: links to external changelogs and, if possible, full diffs

Desired reviewers

@mention

Maintainer checklist

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

• There are at least 2 approvals for the pull request and no outstanding requests for change
• Conversations in the pull request are over OR it is explicit that a reviewer does not block the change
• Changelog entries in the PR title and/or Proposed changelog entries are correct
• Proper changelog labels are set so that the changelog can be generated automatically
• If the change needs additional upgrade steps from users, upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the PR title. (example)
• 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).

[timja]

nice

[MarkEWaite]

I've confirmed that this fixes the Pipeline syntax image on the sidebar of Pipeline jobs. Thanks!

Before (2.335)

After (build of this PR)

Other help icons with issues

I was hoping that this change would also resolve the issue I see with the help icon for the Bitbucket Branch Source plugin. It changes the behavior but does not fully resolve the issue. Would you prefer a separate issue for this one or should it be considered in the context of this pull request?

Before (2.335)

After (build of this PR)

Just in case it is helpful, the inspect for that location looks like this:

[NotMyFault]

I was hoping that this change would also resolve the issue I see with the help icon for the Bitbucket Branch Source plugin

Other help icons of the bitbucket plugins look fine, I guess there's somewhere a left reference to the image path in the bitbucket plugin.

[MarkEWaite]

This PR is now ready for merge. We will merge it after approximately 24 hours if there is no negative feedback.

[NotMyFault]

One zipgrep later and I found your missing icon, Mark
PR is linked above.