Deploy MCAD in agent mode only (without multi-cluster support)

[astefanutti]

WHY

Multi-cluster mode provided by MCAD is experimental and is not used, aside for the purpose of its development.

Even if multi-cluster mode is deactivated by default, a number of resources are installed only for the purpose of its operation.

These resources are used to serve external metrics by the embedded external metrics server, that's not started in single cluster mode, i.e., APIService resources, and a number of ClusterRoleBinding resources, that are irrelevant to the single cluster setup, and introduce noise for security scanning.

WHAT

The CodeFlare operator should not install those resources, as the multi-cluster mode is still experimental and not supported.

HOW

The corresponding resources should be removed from the installation.

Developers working on the multi-cluster mode can use the Helm / Kubernetes manifests available in the MCAD repository.

Once the multi-cluster mode has finalised, and become ready to be supported, the necessary resources and changes will be made to the CodeFlare operator.

TESTS

The e2e tests should pass.