[server, webui, daemons]: Support setting tls secrets by name

[lobis]

Closes #246

Add new field tlsSecretName (unset by default) which can be used to point to a tls secret which will then be used to setup the public/private keys for tls.

I think this provides a cleaner approach compared to asking the user to mount some secrets into some specific paths.

Before this change you would need to do:

  secretMounts:
    - secretFullName: rucio-tls-host-cert
      mountPath: /etc/grid-security/hostcert.pem
      subPath: tls.crt
    - secretFullName: rucio-tls-host-key
      mountPath: /etc/grid-security/hostkey.pem
      subPath: tls.key

After this can optionally be condensed into:

tlsSecretName: rucio-tls-host

Besides the reduced lines of code needed, now (IMHO) it's easier for a new user to figure out how to setup tls from looking at the helm chart.

This change just adds an alternative way to configure tls, the old way still works fine.