Download config of all clusters in a cg for `banzai cluster shell`

[orymate]

Is your feature request related to a problem? Please describe. If you want to use multiple clusters in parallel, you can't use banzai cluster shell easily. You could download the configs to files with banzai cluster shell 'cat $KUBECONFIG' >f, but this is not trivial.

Describe the solution you'd like to see If you execute banzai cluster shell on a cluster which is part of a cluster group, the kubeconfig generated should contain non-default contexts for the other clusters in the group as well.

Describe alternatives you've considered Provide a dedicated config download command.