Use jnr-posix-api plugin

[sarah-witt]

What does this PR do?

Adds jnr-posix-api as a dependency to the plugin and bump the minimum required jenkins version

Description of the Change

Jenkins core removed JNR, and the java dogstatsd client relies on this library. To add the plugin, we need to bump the minimum required jenkins version.

Addresses #285

Alternate Designs

Possible Drawbacks

Verification Process

Additional Notes

The name of the built-in node changed in more recent versions of jenkins, so we will have to update our tests in order to test them in our jenkinsfile: https://www.jenkins.io/changelog-stable/#v2.319.1

Release Notes

Review checklist (to be filled by reviewers)

• Feature or bug fix MUST have appropriate tests (unit, integration, etc...)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have one changelog/ label attached. If applicable it should have the backward-incompatible label attached.
• PR should not have do-not-merge/ label attached.
• If Applicable, issue must have kind/ and severity/ labels attached at least.

[ofek]

LGTM

[basil]

BTW jnr-posix-api is part of the BOM as of https://github.com/jenkinsci/bom/releases/tag/1556.vfc6a_f216e3c6, so once you upgrade to that BOM version (which also requires upgrading to a baseline of 2.319.1 or later) you can remove the <version> from jnr-posix-api and get the version from the BOM instead, which should simplify maintenance.

[sarah-witt]

Thanks for the info @basil! We are going to bump the baseline with this PR so I will make note to do this after that PR is merged.