Add Custom Image Support for MCAD in the CodeFlare Operator

[jbusche]

The ability to update or revert the MCAD image in the MCAD CR will be very helpful going forward.

[anishasthana]

We would want to update the operator, api, and crd: https://github.com/project-codeflare/codeflare-operator/blob/main/api/v1alpha1/mcad_types.go

[astefanutti]

@carsonmh if you plan to work on that, there is #120 that covers the InstaScale controller, and that could be re-used for the MCAD controller, so the approach is consistent.