Operatorless Istio Gateways Certificate Incorrect

Currently, users are able to pass their gateway configurations in directly through the umbrella template in the same format that is described by Istio's documentation:

https://istio.io/latest/docs/reference/config/networking/gateway/#Gateway

However, our logic for creating the certificate secret may end up creating a secret that is different than what is specified in the credentialName portion of the gateway as it will always default to <name>-cert. As a workaround, we can put out a known issue in beta that the credentialName should match that format, however, ideally this should be addressed before we move to beta.

Additionally, the structure its using is an older format and will likely cause issues for anyone trying to use multiple hosts with different certificates on the same gateway.