Export task stream metrics in prometheus

https://github.com/dask/distributed/pull/7088 triggered a discussion around exposing prometheus metrics that include the information to replicate a task stream-like grafana dashboard.
An earlier attempt exposing different information is shown in https://github.com/dask/distributed/pull/7083

Both approaches include valuable information but fall short of actually reproducing what we're looking for. This issue is to track this effort and collect ideas.