libs: improve logging on PG connection errors (#9130)

## Problem
We get some unexpected errors, but don't know who they're happening for.

## Summary of change
Add tenant id and peer address to PG connection error logs.

Related https://github.com/neondatabase/cloud/issues/17336

pageserver/src/page_service.rs

@@ -273,10 +273,20 @@ async fn page_service_conn_main(
                 info!("Postgres client disconnected ({io_error})");
                 Ok(())
             } else {
-                Err(io_error).context("Postgres connection error")
+                let tenant_id = conn_handler.timeline_handles.tenant_id();
+                Err(io_error).context(format!(
+                    "Postgres connection error for tenant_id={:?} client at peer_addr={}",
+                    tenant_id, peer_addr
+                ))
             }
         }
-        other => other.context("Postgres query error"),
+        other => {
+            let tenant_id = conn_handler.timeline_handles.tenant_id();
+            other.context(format!(
+                "Postgres query error for tenant_id={:?} client peer_addr={}",
+                tenant_id, peer_addr
+            ))
+        }
     }
 }
 
@@ -340,6 +350,10 @@ impl TimelineHandles {
                 }
             })
     }
+
+    fn tenant_id(&self) -> Option<TenantId> {
+        self.wrapper.tenant_id.get().copied()
+    }
 }
 
 pub(crate) struct TenantManagerWrapper {