Enable Fuel to make per-environment diagnostic snapshots

Diagnostic snapshot now contains data of all environments that were ever deployed with the particular master node. This way we get huge snapshots which are hard to lookup.

It is required to add ability of making per-environment diagnostic snapshots. It seems that per-environment snapshots should be provided for both existing and deleted environments to cover different debugging/investigation cases.
This feature can co-exist with current all-in-one snapshot.