vm.stop() improvements
vm.stop() improvements

- The `force` parameter is optional and default to `false`.
- If `force` is `true`, always do a hard shutdown.
- Throw `INVALID_PARAMS` when a clean shutdown failed due to missing PV drivers.

lmcro/xo-web,lmcro/xo-web,vatesfr/xo-web,lmcro/xo-web,vatesfr/xo-web