Adapt icon removal from core and bump core requirement to 2.319.3

[NotMyFault]

Fixes JENKINS-67176

The change proposed adapts the icon removal from core and bumps the base line to a modern version of Jenkins.
JSR 305 has been replaced with findbugs annotations, because it's EOL and the bom offers findbugs as replacement.

cc @olamy if you mind taking a look :)

Closes #68 as well

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[NotMyFault]

ci.jenkins.io does not accept Jenkinsfile modifications from foreign PRs on the PR itself, hence the build fails, because it builds with 2.222 instead of 2.319.3.
However, tests are working fine, according to GitHub actions and to my local testing.
Do you mind giving it a review nevertheless, @olamy :)

[boczh]

Hello, just wondering if there is any timeline on approximately when will this PR be merged and new plugin version released?

[NotMyFault]

Hello, just wondering if there is any timeline on approximately when will this PR be merged and new plugin version released?

Anytime, once a maintainer reviews it. In the meantime, you can either build it yourself or use my build binaries: https://keybase.pub/notmyfault_og/jenkins/favorite-plugin/

[olamy]

release done.
sorry guys for delay I have missed the ping (and notifications were lost in a huge stack :( )

[NotMyFault]

No worries, thanks for taking care of it 👍🏻