Running odh command without any subcommands should show the
help message and not execute any functionality. The listing
of namespaces was only added as a test. Make the root
command not runnable and remove the unecessary test.

Using the generated model registry REST client for the cli
purposes can be quite tedious. The cli only requires a subset
of the functionality.

Add a client facade with the needed functionality only for
listing models and creating a registered model, a model version
and a model artifact.

Using the model registry to implement the edge use case
includes a lot of custom logic. Add an edge client abstraction
that encapsulates such logic which can be used by the CLI
directly. Start by adding listing and adding models.

Using the introduced edge client, refactor the model command
to simply use the edge client for listing and adding models.

Also refactor the commands design to streamline the flags
and commands initialization.