Merge topic branch t/completion into next

Merge topic branch t/completion into next

The completers for para_client and para_audioc handle some cases
incorrectly or not at all. This series improves on that.

Started on 2025-04-07.

* refs/heads/t/completion:
  Revamp bash_completion.
  bash completion: Fix help option parsing.
  audioc: Fix option completion of version and stat.
  i9e: Introduce i9e_get_nonopt_argnum().
  i9e: Introduce i9e_cword_is_option_arg().
  i9e: Constify i9e_complete_option().