Replace PNG icons with SVGs

[NotMyFault]

The change proposed exchanges the PNG icons with SVG icons, to integrate better with the modern appearance of Jenkins:

• 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
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[NotMyFault]

Heyo @LinuxSuRen,
do you mind taking a look? Would be nice to have this one available as well on the next LTS, which focuses a lot on UI improvements.
Thanks in advance!

[jetersen]

@NotMyFault should the jenkins version be bumped?

[NotMyFault]

@NotMyFault should the jenkins version be bumped?

If you want to, though this works even on an older baseline.

[jetersen]

Thanks @NotMyFault all I wanted to know 😄