storage: add http/https server and cert resover metrics (#11450)

## Problem
We need to export some metrics about certs/connections to configure
alerts and make sure that all HTTP requests are gone before turning
https-only mode on.
- Closes: https://github.com/neondatabase/cloud/issues/25526

## Summary of changes
- Add started connection and connection error metrics to http/https
Server.
- Add certificate expiration time and reload metrics to
ReloadingCertificateResolver.

storage_controller/src/main.rs

@@ -472,6 +472,7 @@ async fn async_main() -> anyhow::Result<()> {
             let https_listener = tcp_listener::bind(https_addr)?;
 
             let resolver = ReloadingCertificateResolver::new(
+                "main",
                 &args.ssl_key_file,
                 &args.ssl_cert_file,
                 *args.ssl_cert_reload_period,