[sonatype-nexus] Improve ingress tls hosts configuration

[mlallaouret]

The issue with the current configuration is that we need to define a complete hosts block in the value file like for example:

ingress:
  tls:
    hosts:
      - hosts:
        - <yourDomain>
        secretName: <yourTlsSecret>

More, if you do not use the nexus proxy, it results with an tls block like the following:

tls:
  - hosts:
    secretName: "nexus-tls"
  - hosts:
    - <yourDomain>
    secretName: <yourTlsSecret>

This PR allows to define the proxy host or the direct host tls configuration in the same block.
I think that if someone need to have the proxy host and the direct host configuration, maybe the chart needs something like a new property named additionalTls

Downside: This is a breaking change for those who were specifying the ingress.tls.hosts value. I did not change the version in the Chart.yaml as I did not know if it would be a 6.0.0 or something else.

Feel free to tell me if I miss something.