[FEAT] Display the name of the builder that ran the test

[aptalca]

Is this a new feature request?

• I have searched the existing issues

Wanted change

It would be nice if the ci test result lists the name of the builder that ran the test.

Reason for change

• There are some significant differences between hetzner and contabo ones in terms of timings
• If we get a bunch of builds fail, we may be able to spot an issue with an individual builder much more easily by simply clicking through ci reports in the discord channel

Proposed code change

Accept an env var where the builder name can be passed as a value, and display it in the ci test result. Jenkins automatically sets the var NODE_NAME and we use that to display it in the build logs: https://github.com/linuxserver/docker-jenkins-builder/blob/master/roles/generate-jenkins/templates/Jenkinsfile.j2#L43
We only need to display the amd64 builder because the entire test runs on there.
An issue with an arm builder would likely result in a build failure rather than a test failure.