Show latency on workspace view

[matifali]

Display latency for each workspace.

[ethanndickson]

We're yet to decide on a way to implement this, as we can either perform the ping:

• In the Go code, and send the results over the tunnel
• In the Swift code, pinging the hostname directly

The latter doesn't provide us a way to also collect whether the connection is DERP or P2P - we'd need to determine that by pinging within the Go code. If we want to also indicate that eventually, it'd be beneficial to do the former, but it makes closing this issue more difficult.