Feature Request: Add support for CORS configuration

[JakeNeyer]

Context:
As kserve is moving to it's v2 api, it's defaulting the server images to ml-server. It looks like kserve and knative are pushing off adding CORS configurations on their CRDs due to complexity (knative/serving#10040). The simplest way I have seen to get around that is adding an OPTIONS route and CORS options on the actual servers themselves.

Request
Add OPTIONS routes and the ability to apply runtime configuration for CORS on the MLServer

[adriangonz]

Fixed by #387