`set-credentials` command can also be used to config kubeconfig with credentials
exec plugins. However, there is no flag provided by this command to set
`InteractiveMode` and `ProvideClusterInfo` fields in credentials exec plugins.
Since `InteractiveMode` is required field, this makes the command's output
is incomplete and invalid. This PR introduces 2 new flags in set-credentials
command to let users can configure these 2 fields in credentials exec plugins,
especially the one `InteractiveMode` which is required.
Kubernetes-commit: b088e65007761bda1aee0b5fb92f79d1aae82c05