This PR replaces NGINX and Certbot with Caddy.
1. Auto-HTTPS when custom domain is set, is handled by Caddy.
2. If past certs exist, that were provisioned by Certbot in older
Appsmith versions, we configure Caddy to make use of them. But this only
applies if the certs aren't already expired. If they're expired, point 1
applies.
3. If custom certs are provided in `ssl` folder, Caddy will be
configured to use them.
4. Incoming `Forwarded` header is not passed to any reverse proxies. So
redirect URL is correctly computed on Google Cloud Run.
5. All other route configurations are exactly as they are in NGINX
today.
Caddy configuration file is generated in the `caddy-reconfigure.mjs`
script, which will also reload Caddy with the new configuration.
