ENH for `AzureVMCluster`: timeout?

One of the really nice `AzureMLCluster` features was a timeout option (`scheduler_idle_timeout`). Is that something it might be possible to port to `AzureVMCluster`? I work a lot with students, and it's a guardrail I find really useful for them to have. There's currently a "Shutdown the VM if the Dask process exits." option, but no "kill an idle cluster" option that I see.