Autoscaled cluster costs

**Background**
At the moment, Cloud Pipeline allow to view a price estimation for the `single` instance jobs and `static` clusters.
But the auto-scaled clusters do not provide such information. Users see a price only for a master node.

This feature shall be added, as the auto-scaled clusters are used at most.

**Approach**
* Compute the estimated price for all the cluster (including static and auto-scaled) in the backend
* Price is computed based on all the `RUNNING` instances, which are children of the particular master. Plus the mater's price (note: worker nodes can be of different instance size than a master)
* This information shall be stored in the master `run`
* Estimated price shall be updated on a scheduled basis (default: 30 seconds)
* GUI shall use this new `run`'s attribute to display estimated cost for the cluster (for the `static` as well)