[sdargoeuves]

Configurable timeout for the lab status file lock

When running many lab instances in parallel with the multilab plugin (20 at the same time in my case), some netlab up commands fail because they can't get the lab status file lock within the hard-coded 3-second timeout:

Fatal error in netlab: Cannot lock lab status file /home/sa/.netlab/status.yaml.lock
... <class 'filelock._error.Timeout'>

This PR adds the defaults.lab_status_lock_timeout parameter (in seconds) to change that timeout. Without it, the timeout stays at 3 seconds:

defaults.lab_status_lock_timeout: 10

The parameter is documented in the multilab plugin documentation, next to defaults.lab_status_file. I haven't got any validation on this value, not sure if it's worth it (I had it initially, but it seemed a bit of an overkill).

Context: I'm working on a way of running several integration tests at the same time using the multilab plugin. I'll open a discussion on this topic.

[sdargoeuves]

this might be useless... I had some problems when starting 20 or more labs at the same time, for which I thought changing this value could help, but it doesn't seem to be the case.
Back to draft, and potentially, I will close the PR.