Support setting `spec.ingressClassName` on Ingress resources

Support setting spec.ingressClassName on Ingress objects:

spec:
  ingressClassName: xyz 

According to the table on ingress resources, GitLab ingress resource stopped working with ingress controller helm chart from version 4.0.0++ , but it working properly with ingress controller 3.39 which is the latest ingress controller that work with the flag "ingressclass ", ingress controller with helm chart 4.0.0++ start working with .spec.ingressClassName.

https://github.com/kubernetes/ingress-nginx/tree/main