[enhancement]: Add a predefined variable for stage name where the resource trigger is a pipeline with a stage trigger

[jabbera]

Describe your feature request here

When triggering with a resource pipeline and a stage filter it would be very helpful to have the stage name that triggered the pipeline as part of the predefined variable list: https://learn.microsoft.com/en-us/azure/devops/pipelines/yaml-schema/resources-pipelines-pipeline?view=azure-pipelines#pipeline-resource-metadata-as-predefined-variables

[vmapetr]

Hi @jabbera, thanks for reporting! We are working on more prioritized issues at the moment, but will get back to this one soon.

[github-actions[bot]]

This issue has had no activity in 180 days. Please comment if it is not actually stale

[jabbera]

Not stale.