Generate MCAD clients

[astefanutti]

The existing clients in pkg/client are not up-to-date, and do not follow current client-go standards / conventions.

The client is already being used internally by MCAD for the informers, in the CodeFlare operator e2e tests, and is plan to be used in the KubeRay integration.

As the AppWrapper API is a public / user-facing API, it's important the corresponding client be up-to-date and readily available, for downstream projects to consume.

The best way to achieve this is to continuously generating the clients from the APIs.

[z103cb]

@astefanutti I have followed the example set in this PR to generate the clients.

Unfortunately the generated code will require upgrading to higher version of the k8s. I have attempted to do so in a previous PR #344. That work points to issues with the metrics adapter code used to expose cluster metrics for the 'Multi Cluster' function.

I propose we differ this work until the k8s is upgraded.

@anishasthana, @accorvin and @tardieu

[astefanutti]

@z103cb an option may be to adapt the code-generator version, so its k8s dependencies align with the current version used by MCAD.