[request] Lazy psutil import

[mh0g]

Is your feature request related to a problem? Please describe.
When using meshroom_compute we don't have the dependencies of meshroom with ui, except for psutil which is used to monitor resources.

Describe the solution you'd like
Ideally we would like to lazily import psutil and only monitor resources when its available.

Describe alternatives you've considered
To the best of my knowledge there is no native package in python to monitor ressources

Additional context
meshroom_compute is used to run graphs without ui, and in the plugin system