Add the job name as tags on collected metrics

Since NXBT-3742 we can monitor our CI.
For some widgets it could be useful to know the job behind the collected metrics, for instance this is the case for widgets that follow the duration of builds.

On nuxeo-lts for instance, we have several jobs in the repository, build, javadoc, release, with different duration.

There's the environment variable JOB_BASE_NAME available on a regular pipeline job.
On a multi branch pipeline job, the JOB_BASE_NAME seems to hold the branch name on which it is executed. The environment variable JOB_NAME could be used, but it contains the whole job path, for example: nuxeo/lts/nuxeo/2023.

In both cases, we could probably extract the job name value from WORKSPACE or something else.

Or, the name of the Groovy file, e.g. build.groovy.

Needed for the Jenkins runner, and also the deployed environment, e.g. unit tests.