fvm list <CHANNEL> should list artifact versions in that channel

[digikata]

Current fvm list will list channel/versions of package sets:

$ fvm list
    CHANNEL               VERSION                                             
 ✓  stable                0.11.4                                              
    latest                0.11.5-dev+04967f76d9228a7c343feb90742047080eddf873 

With an option argument provided, the artifact versions should be listed (like they are during install)

$ fvm list stable
Artifacts in channel "stable" version "0.11.4"
fluvio@0.11.4
fluvio-cloud@0.2.17
fluvio-run@0.11.4
cdk@0.11.4
smdk@0.11.4

---

For ref during install:

$ fvm install stable
info: Downloading (1/5): fluvio@0.11.4
info: Downloading (2/5): fluvio-cloud@0.2.17
info: Downloading (3/5): fluvio-run@0.11.4
info: Downloading (4/5): cdk@0.11.4
info: Downloading (5/5): smdk@0.11.4
done: Installed fluvio version 0.11.4
done: Now using fluvio version 0.11.4