This patch allows tls to be enabled with an empty secretName for ingress controllers might be able to provide a default certificate.
Fixes#5858, provides better defaults for the Ingress object and allows TLS to be enabled with an empty secretName.
### Motivation
The current helm chart can create an Ingress with TLS, but it requires a secretName to be added. This is not an Ingress requirement and, in some cases, the ingress controller can provide a default certificate when the Ingress object does not declare one.
### Modifications
Modifications include `values.yaml` and `dashboard-ingress.yaml` to address the issue.
Allows to opt-in for an ingress on top of the dashboard service.
This is very important in production-grade deployments where
you want to expose the Pulsar dashboard through an easy to remember URL.
