Execute SSH readiness check in 'netlab initial'

[ipspace]

No description provided.

[ipspace]

It turns out that it's unsafe to configure cEOS container before its SSH server is ready. As I wanted to be able to configure them without Ansible, I had to implement the "SSH readiness" check in Python (in netlab initial). This PR implements the core functionality; there are still a few rough edges that will get polished after merging this one. For example, there's no need to repeat the test in the Ansible playbook.

Comments (including the usability of the feature) are highly recommended.

[Copilot]

Pull request overview

Adds an SSH-based device readiness check that runs as part of netlab initial configuration deployment.

Changes:

• Extends netlab initial --debug options to include an ssh debug flag.
• Introduces a new SSH readiness implementation (netsim/cli/initial/ready.py) and a dispatcher for readiness steps based on netlab_ready.
• Invokes readiness checks from netlab initial deployment flow before configuration deployment.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
netsim/cli/initial/utils.py	Adds ssh to the hidden debug choices so SSH readiness diagnostics can be enabled.
netsim/cli/initial/ready.py	Implements the SSH readiness check and a device_ready() dispatcher keyed off netlab_ready.
netsim/cli/initial/deploy.py	Calls ready.device_ready() before pushing configurations to devices.

[ipspace]

there are still a few rough edges

Speaking of rough edges: interrupting "netlab up" (which calls "netlab initial") with ctrl/c while we're waiting for SSH servers works (as in "kills everything and gets back to bash prompt") but does not generate the "user interrupted.." message even though the code is already wrapped into try/except KeyboardInterrupt block in the netlab/initial run function.

Any potential solution would be highly appreciated ;) /cc @Muddyblack