Azure CLI needs to be able to delete pipeline runs

**Is your feature request related to a problem? Please describe.**
During testing, I sometimes create a _lot_ of runs and artifacts. I can easily exceed how much storage I have available in a single _day_.

**Describe the solution you'd like**
The following command should delete a run including all artifacts.
az pipelines runs delete --id [int]

**Describe alternatives you've considered**
Right now, the only way to delete a run is to manually go to the website and delete it individually. Doing this manually for dozens of runs is painful.