storcon: reuse reqwest http client (#11327)

## Problem

- Part of https://github.com/neondatabase/neon/issues/11113
- Building a new `reqwest::Client` for every request is expensive
because it parses CA certs under the hood. It's noticeable in storcon's
flamegraph.

## Summary of changes
- Reuse one `reqwest::Client` for all API calls to avoid parsing CA
certificates every time.

storage_controller/src/service/safekeeper_reconciler.rs

@@ -338,7 +338,6 @@ impl SafekeeperReconciler {
             .safekeeper_jwt_token
             .clone()
             .map(SecretString::from);
-        let ssl_ca_cert = self.service.config.ssl_ca_cert.clone();
         loop {
             let res = req
                 .safekeeper
@@ -347,8 +346,8 @@ impl SafekeeperReconciler {
                         let closure = &closure;
                         async move { closure(client).await }
                     },
+                    self.service.get_http_client(),
                     &jwt,
-                    &ssl_ca_cert,
                     3,
                     10,
                     Duration::from_secs(10),

storage_controller/src/service/safekeeper_service.rs

@@ -78,8 +78,8 @@ impl Service {
         for sk in timeline_persistence.sk_set.iter() {
             let sk_id = NodeId(*sk as u64);
             let safekeepers = safekeepers.clone();
+            let http_client = self.http_client.clone();
             let jwt = jwt.clone();
-            let ssl_ca_cert = self.config.ssl_ca_cert.clone();
             let req = req.clone();
             joinset.spawn(async move {
                 // Unwrap is fine as we already would have returned error above
@@ -90,8 +90,8 @@ impl Service {
                             let req = req.clone();
                             async move { client.create_timeline(&req).await }
                         },
+                        &http_client,
                         &jwt,
-                        &ssl_ca_cert,
                         3,
                         3,
                         SK_CREATE_TIMELINE_RECONCILE_TIMEOUT,