cmd_runner_fmt.as_fixed() now accepts list of args (#9893)
* cmd_runner_fmt.as_fixed() now accepts list of args
* update CmdRunner guide
* add changelog frag
* Update changelogs/fragments/9893-cmdrunner-as-fixed-args.yml
* fix overdoing in as_fixed()
(cherry picked from commit 9286b60182)
Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>