feat(jenkins-jobs) add GitHub scm custom notification to ensure distinct checks for each job

[dduportal]

Ref. jenkins-infra/helpdesk#2778 (comment)

This PR proposes the following:

GitHub checks default notification is changed from continuous-integration/jenkins/pr-merge to the following pattern:

jenkins/<Jenkins FQDN>/<Full Job Identifier> where:

• is passed by helm values or defaults to "localhost"
• is automatically set to the full Jenkins internal Job ID (string with '/' separators when recursive job structure such as folders or multibranch jobs)

Example with a diff on the infra.ci.jenkins.io setup:

• Principal job for jenkins-infra/packer-images:

+                       gitHubNotificationContextTrait {
+                         contextLabel('jenkins/infra.ci.jenkins.io/infra-tools/packer-images')
+                         typeSuffix(true)
+                       }

• Secondary (updatecli) job for jenkins-infra/packer-images:

+                       gitHubNotificationContextTrait {
+                         contextLabel('jenkins/infra.ci.jenkins.io/updatecli/packer-images')
+                         typeSuffix(true)
+                       }

Pros:

• Less configuration: the notifications for secondary jobs do NOT require a custom static string (like the current GH check "Updatecli (infra.ci.jenkins.io)" check name on each job
• Supports more than 2 multibranch jobs per repository

Cons:

• Naming depends on the Jenkins controller structure: it changes per repository

[lemeurherve]

👏