Add a tag to select an appropriate executor for a heavy task

The different executors available run on servers with different hardware characteristics. In addition, some of these servers are dedicated to CI/CD while others run other services. This variability prevents any objective analysis of variations in performance measurements. To remedy this, I propose to associate a heavy-task tag with the measure job, which is only declared on the Kubernetes executor. This cluster uses a node pool with identical hardware characteristics, dedicated to CI/CD. This will make the results more meaningful.