generate command does not recognize `-n` flag anymore

[FloSch62]

The generate command docs are currently having non working examples

containerlab gen -n 3tier --nodes 4,2,1
Error: unknown shorthand flag: 'n' in -n

Also it add non schema vars, like settings: null and debug: false

containerlab gen --name 2tier --nodes 2,1  
name: 2tier
prefix: null
mgmt: {}
settings: null
topology:
  nodes:
    node1-1:
      kind: srl
      group: tier-1
    node1-2:
      kind: srl
      group: tier-1
    node2-1:
      kind: srl
      group: tier-2
  links:
  - endpoints:
    - node1-1:e1-1
    - node2-1:e1-1
  - endpoints:
    - node1-2:e1-1
    - node2-1:e1-2
debug: false

Not sure how much the command is used, maybe it even makes sense to remove it?

[hellt]

still useful to have it, worth fixing