Add `DevfileRegistry` CRD field for setting the ingress class

[michael-valdron]

Which area/kind this issue is related to?

/area registry

Issue Description

The registry operator is missing a field to set the ingress class name https://github.com/devfile/registry-operator/blob/f55ab8e7c8061934547c7d55bd67d81d509a8752/api/v1alpha1/devfileregistry_types.go#L117, which is what the helm chart has: https://github.com/devfile/registry-support/blob/f66264f22310c3c93bf0c77db5f4cd4b560aba5e/deploy/chart/devfile-registry/values.yaml#L18

Parent Epic: #1274

Acceptance Criteria

• Implement DevfileRegistry.K8s.IngressClass field
• Create test case to set DevfileRegistry.K8s.IngressClass field
• Run integration tests to verify changes

[thepetk]

As discussed this item will not be covered during this sprint so it will be moved to the next one (2257)