feat: add a balance command

[ylmrx]

 pvecontrol -c dev balance --rich-display --anti-affinity test,VM --anti-affinity-tags 'my-tag' --help           
Usage: pvecontrol balance [OPTIONS]

  Balances VMs across nodes in the cluster, bear in mind the model used won't
  give the same result upon every calls

Options:
  -a, --anti-affinity TEXT        Balance machines with comma-separated
                                  patterns across nodes
  -t, --anti-affinity-tags TEXT   Balance machines with comma-separated tags
                                  across nodes
  -p, --movement-penalty INTEGER  Higher values minimize VM movements
  -r, --running                   Balance only the currently running instances
  -R, --rich-display              Use rich display
  --timeout FLOAT                 Limit calculation time, tiny values will
                                  result in sub-optimal solution
  --overcommit FLOAT              Sets an overcommit ratio regarding CPU nodes
                                  requirements
  --help                          Show this message and exit.

• Uses ortools https://or-tools.github.io/docs/pdoc/ortools.html to constrain and solve balancing of basic VMs across many nodes.
• Can use anti-affinity with name patterns and tags
• Can overcommit (cpu), and deal with movement penalty (to move as few VM as possible)

Anti-affinity definitions could happen in config.yaml too