Add pipeline-groovy-lib

[jglick]

Supersedes #1166. See JENKINS-57023, inspired by gratuitous dependencies in test classpaths: #1159 (comment)

Picks up:

• [JENKINS-57023] Retain only deprecated global library functionality workflow-cps-global-lib-plugin#172
• [JENKINS-57023] Switch dep from workflow-cps-global-lib to pipeline-groovy-lib pipeline-model-definition-plugin#530
• [JENKINS-57023] Switch dep from workflow-cps-global-lib to pipeline-groovy-lib workflow-multibranch-plugin#180

Might also benefit from test-only dep fixes:

• [JENKINS-57023] Switch dep from workflow-cps-global-lib to pipeline-groovy-lib configuration-as-code-plugin#1973
• [JENKINS-57023] Switch dep from workflow-cps-global-lib to pipeline-groovy-lib git-plugin#1274
• [JENKINS-57023] Switch dep from workflow-cps-global-lib to pipeline-groovy-lib github-branch-source-plugin#565

If all of those are integrated, I believe we could remove workflow-cps-global-lib from the managed set. At that point we may as well remove git-server as well, and could consider removing sshd.

[jglick]

Note that workflow-cps-global-lib currently still has a 2.303.x dep, so on the 2.289.x line it is still pinned (#788). This seems to cause some weird behavior in that e.g. https://ci.jenkins.io/job/Tools/job/bom/job/PR-1168/5/testReport/org.jenkinsci.plugins.workflow.libs/FolderLibrariesTest/ runs tests twice on 2.289.x, but appears harmless for now. Could be cleaned up if desired by porting jenkinsci/pipeline-groovy-lib-plugin#5 to the deprecated plugin.