[Feature Request] Add Command Return Supported K3s Version

[Jason-ZW]

• Add Command Return Supported K3s Version.
• UI better use drop-down component show which K3s version can be selected. e.g.

autok3s k3s-versions

[orangedeng]

K3s has tons of versions and maybe we don't need all of them. I suggest that we can do this like nvm.

To show a list of latest version of each channel. And the user can just select one of them.

Most of the info we need can be found in https://update.k3s.io/v1-release/channels so I think we can do it in a simple way.