Component(s)

AlertManagerConfig

What is missing? Please describe.

RocketChat receiver was added in alertmanager config secret in #7315

To make it supported in CRD level as well support it in AlertmanagerConfig CRD as well

Needs alertmanager >= v0.28.0
See https://github.com/prometheus/alertmanager/pull/3600/files

Describe alternatives you've considered.

No response

Environment Information.

Environment

Kubernetes Version:
Prometheus-Operator Version: