Adding run-action for all units in a model (or application)

Hi, I came across and I see it’s marked as a duplicate of Bug #1714791 “juju run --all-units” : Bugs : Canonical Juju but that one is about run rather than run-action. Can we unmark the former as a duplicate of the latter? It’s something I’d find useful.

Done. Note that run-action has become run in Juju 3.0+, and run has become exec.