k/connection_context: replaced node hash map with chunked hash map

Replaced `node_hash_map` keeping state of virtualized connections with
`chunked_hash_map`. The change will allow us to avoid large allocations
when dealing with large virtual connection number.

Signed-off-by: Michał Maślanka <michal@redpanda.com>

src/v/kafka/server/connection_context.cc

@@ -720,13 +720,14 @@ connection_context::dispatch_method_once(request_header hdr, size_t size) {
       "request from virtual connection {}, client id: {}",
       client_connection_id.v_connection_id,
       client_connection_id.client_id);
-    auto it = _virtual_states.lazy_emplace(
-      client_connection_id.v_connection_id,
-      [v_connection_id = client_connection_id.v_connection_id](
-        const auto& ctr) mutable {
-          return ctr(
-            v_connection_id, ss::make_lw_shared<virtual_connection_state>());
-      });
+
+    auto it = _virtual_states.find(client_connection_id.v_connection_id);
+    if (it == _virtual_states.end()) {
+        auto p = _virtual_states.emplace(
+          client_connection_id.v_connection_id,
+          ss::make_lw_shared<virtual_connection_state>());
+        it = p.first;
+    }
 
     co_await it->second->process_request(
       shared_from_this(), std::move(rctx), sres);

src/v/kafka/server/connection_context.h

@@ -11,6 +11,7 @@
 #pragma once
 #include "base/seastarx.h"
 #include "config/property.h"
+#include "container/chunked_hash_map.h"
 #include "kafka/server/fwd.h"
 #include "kafka/server/handlers/handler_probe.h"
 #include "kafka/server/logger.h"
@@ -437,7 +438,7 @@ class connection_context final
      * A map keeping virtual connection states, during default operation the map
      * is empty
      */
-    absl::node_hash_map<
+    chunked_hash_map<
       virtual_connection_id,
       ss::lw_shared_ptr<virtual_connection_state>>
       _virtual_states;