Extend kubectl plugin to support commands for ClusterExtensions including:
- list : list currently installed ClusterExtensions with useful information including status
- get : get info on an existing ClusterExtension
- install : create a ClusterExtension for a package using an existing ServiceAccount, with relevant optional constraints (version, channel etc.)
- uninstall : remove the ClusterExtension for a package
- upgrade : update the ClusterExtension for a package for a provided version/channel etc.
- list-available : list bundles available to be installed with support for relevant constraints (package, channel, version range/version, catalog label selectors etc.)