Bring your own envoy gateway

Hey there, cool project :)

I noticed that the gateway resource defined by your helm chart is hard coded to HTTP. To mitigate this, I wanted to bring my own envoy gateway with HTTPS and hostname configured, but it seems to me I cannot just "plug" it into the AIBrix setup. There is the option to disable the builtin gateway. But that also disables the HTTPRoutes. Ideally, the helm chart would allow me to pass the name of my gateway and use that in setting up the HTTPRoutes. But I am unsure about the implications for the gateway plugins.

What do you think?

Start by inspecting the Helm chart's gateway resource, HTTPRoute templates, and gateway plugin configuration, then trace the path used when the built-in gateway is disabled. Done means the chart accepts a user-provided gateway name, keeps the HTTPRoutes enabled, and preserves compatible gateway plugin behavior.

Written by the indexing model from the issue text.