[JENKINS-66438] replace png with svg icons (ionicons)

[mawinter69]

alternative to #89

refer to ioniocons-api plugin when a suitable symbol is available
Use <l:icon instead of <img
This works for both symbols and images provided by plugins

The difference to #89 is that there the gray color is hard coded. Here I use currentColor so that the actually used color is selected by the theme, that ensures compatibility with other themes.

bumps core to 2.361.4 which requires java11

the symbols in the Cause Column respect the table sizing when only the icon is shown and are shown in one line. Otherwise small icons are used, with each cause on a separate line (see JENKINS-71264)

Testing done

Submitter checklist

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

[NotMyFault]

I welcome this change very much! Although the build failed temporarily because the Jenkinsfile modifications aren't trusted, but this shouldn't block a review 🚀

[mawinter69]

Now that dark theme plugin made it to the recommended plugins in the installation wizard this PR becomes more urgent as before. The plugin is really giving a bad user experience with dark theme.
@batmat I know you consider this your baby, but I think it is time now that the baby moves forward and doesn't ignore reality.

[cronik]

Would love to see this PR merge to align it with latest Jenkins design system. The current icons and tooltips looks weird when used with other updated badges.

Is this plugin up for adoption since there doesn't seem to be any activity in a while?

[cronik]

Been running a build of this PR in a number of Jenkins instances (2.452.1) for a few weeks. Looks nice in both light and dark themes.