Add commands `ockam node start` and `ockam node stop`

[mrinalwadhwa]

We currently have node commands

ockam node create green

and

ockam node delete green

We also need

ockam node start

and

ockam node stop

so that a node can be started and stopped without losing its identity and other state.

[BeenzSyed]

@spacekookie, should this be reassigned to someone else on the team? I remember you had completed the Rust side of starting and stopping a node and it's unblocked for it to be added to the Ockam CLI.

[spacekookie]

I think this issue is basically done, see #3111