Modernize plugin

[basil]

No description provided.

[basil]

Used my admin powers to replay the build with the Jenkinsfile changes here: https://ci.jenkins.io/job/Plugins/job/structs-plugin/job/PR-167/2/

[car-roll]

@basil does this need to be released?

[basil]

I can't recall what I was doing at the time I filed this PR and whether or not it needed a release, but a release couldn't hurt I think.

[tumaf33]

hi @basil - this PR/release have impacted our Jenkins that was running with old version (Jenkins 2.235).
After a service restart for Jenkins, struct plugin couldn't be loaded and as a result pipeline plugin, credentials plugin and others couldn't be loaded too as well as jobs, and it has impacted our whole system.

Here is the relevant snippet you would like to see:

 Failed Loading plugin Structs Plugin v325.vcb_307d2a_2782 (structs)
java.io.IOException: Failed to load: Structs Plugin (325.vcb_307d2a_2782)
 - Jenkins (2.361.4) or higher required

If some people is still using the old version, it will impact them.