[FEATURE] stop all workspaces

[brandonbloom]

Is your feature request related to a problem? Please describe.

Sometimes, I work on a few separate projects and forget to tidy up after myself. I wind up with multiple workspaces and leave them all running. I'd like some way to shut them all down quickly.

Describe the solution you'd like

One idea is something like exo workspace foreach stop, which would run the stop command in each workspace (this foreach command does not exist at time of writing this comment), though stopping seems common enough to have some builtin shorthand for it.