[self-hosted] [helm] allow the use of Kubernetes TLS secrets for http-certs

[cyrilcros]

Hi, I am closing #3199 and opening this instead after adding more stuff on my own git fork...
I just realized I had forgotten about the registry facade which is not a preview anymore; that should now work....

Anyway:

• fixes kubernetes.io/tls certificate support for certificatesSecret #3183
• you don't have to package your certificate manually, which helps for cert-manager and other such tools
• I check if fullchain.pem and privkey.pem are in the certificatesSecret secret; if they are I accept them and ask in the NOTES.txt to switch to using Kubernetes TLS Secret ; otherwise I assume they have tls.crt tls.key.

[pkalemba]

+1 need this :)

[cyrilcros]

@pkalemba Thanks, I am pretty sure this branch will be superseded by https://github.com/gitpod-io/gitpod/compare/aledbf/proxy2caddy which already uses tls.crt / tls.key.

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.