Remove unused image assets

[janfaracik]

Proposed changelog entries

• Remove superfluous user interface elements, including images, mask-icon, and unnecessary resize handles.

What's changed?

• Removed a fair few unused assets from Jenkins/combined assets where possible to cut down on space
• Removed mask-icon - https://www.leereamsnyder.com/blog/favicons-in-2021 - Jenkins now has a lovely colourful icon on Safari ❤️
• Textareas no longer have superfluous resize handles on browsers that support resize (anything that's not IE11)

Screenshots

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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).

[jglick]

Have you searched plugin sources to make sure there are no users of the small icons proposed for deletion?

[janfaracik]

Have you searched plugin sources to make sure there are no users of the small icons proposed for deletion?

Had a scan through and there's a few that are in use by extremely old plugins (eg ten years old) that haven't had any updates. The only plugin that I found that has recent updates is https://github.com/jenkinsci/release-plugin - it's currently using the atom.gif icon, I'd be happy to make an MR for it to use the new RSS icon currently used by Jenkins

[timja]

tbh can't even remember why I touched that plugin, I assume to do with tables to divs but I can't tell now =/. I can merge and release it by the looks of it though.

[timja]

Looks good just needs release plugin sorted from what I can see

[janfaracik]

Looks good just needs release plugin sorted from what I can see

Just opened a PR for that - jenkinsci/release-plugin#36 :)

[fqueiruga]

Nice. off topic, I think I should create a PR to remove the experimental header we introduced... 2 years ago 😅

[fqueiruga]

Nice. off topic, I think I should create a PR to remove the experimental header we introduced... 2 years ago 😅

[timja]

Nice. off topic, I think I should create a PR to remove the experimental header we introduced... 2 years ago 😅

Yeah probably, not worth keeping that tech debt around since it was never enabled by default

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

Thanks!

[daniel-beck]

Caused JENKINS-69319.