Problem
The OIDC discovery URL for kubernetes https://kubernetes.default.svc/.well-known/openid-configuration does not work in every distribution, for example in EKS (see aws/containers-roadmap#2234). For now, we should work around this by allowing users to set this discovery url themselves in the config-features configmap.

This can be a field in the configmap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: config-features
  namespace: knative-eventing
data:
  oidc-discovery-url: https://kubernetes.default.svc/.well-known/openid-configuration # or something else, this is just the default

Persona:
Which persona is this feature for?

Any user wanting OIDC in EKS

Exit Criteria
A measurable (binary) test that would indicate that the problem has been resolved.

Time Estimate (optional):
How many developer-days do you think this may take to resolve? 1-2

Additional context (optional)
Add any other context about the feature request here.

This should fix the root cause of knative-extensions/eventing-kafka-broker#3901