Provide Java implementation to list available icons

[strangelookingnerd]

What feature do you want to see added?

I'm not 100% sure if this is the right place, might be more of a core topic:

Similar to org.jenkins.ui.icon.IconSet there should be a way to list all available icons.
Right now I'm trying to implement a new feature for my plugin to use the icons provided here as folder icons (see jenkinsci/custom-folder-icon-plugin#84 / jenkinsci/custom-folder-icon-plugin#85).

My solution is very hacky (https://github.com/jenkinsci/custom-folder-icon-plugin/pull/85/files#diff-b39cabcc52a769a78a09036dde7121d7a62dcb6c0344a02fd3461eddb29380a7R133-R167) and currently only takes "ionicons" into account. However it would be great to extend this to include "all built-in icons". As I understood it should be convention to add custom icons in the resource path of images/symbols. So it should be rather easy to scan for any svg resources in classpath.

Any thoughts would be appreciated and I'd be happy to provide follow-up PRs (with a less hacky solution...).

Upstream changes

No response