Spawn workspace SSH connection only on selection in environment list in new Toolbox architecture

[Kira-Pilot]

Within the new Gateway, an open workspace is maintained as an active connection. This means that a workspace is essentially 'started', even if one isn't actually making use of it. As a result, workspace activity is inaccurate and features like autostart/autostop are compromised.
We should find a way to spawn SSH connections only on click or selection.

Hopefully, this can be done with JetBrains' existing API; if not, we should consider reimplementing the environment list from scratch. See #423 for additional detail on the environment list; there is a discussion about re-implementing from scratch in that ticket, as well.