db: extract loaded_endpoint_state into a lightweight header

Move loaded_endpoint_state from gossiper.hh to
gms/loaded_endpoint_state.hh so db/system_keyspace.hh no longer needs the
full gossiper header.

Add direct gossiper includes at the remaining users that still need it.

db/system_keyspace.hh

@@ -15,10 +15,11 @@
 #include <utility>
 #include <vector>
 #include "db/view/view_build_status.hh"
-#include "gms/gossiper.hh"
+#include "gms/inet_address.hh"
+#include "gms/generation-number.hh"
+#include "gms/loaded_endpoint_state.hh"
 #include "schema/schema_fwd.hh"
 #include "utils/UUID.hh"
-#include "query/query-result-set.hh"
 #include "db_clock.hh"
 #include "mutation_query.hh"
 #include "system_keyspace_view_types.hh"
@@ -36,6 +37,10 @@ namespace netw {
     class shared_dict;
 };
 
+namespace query {
+    class result_set;
+}
+
 namespace sstables {
     struct entry_descriptor;
     class generation_type;

db/view/view.cc

@@ -29,6 +29,7 @@
 
 #include "db/config.hh"
 #include "db/view/base_info.hh"
+#include "query/query-result-set.hh"
 #include "db/view/view_build_status.hh"
 #include "db/view/view_consumer.hh"
 #include "mutation/canonical_mutation.hh"

db/view/view_building_coordinator.cc

@@ -13,6 +13,7 @@
 #include <seastar/core/abort_source.hh>
 #include <seastar/coroutine/parallel_for_each.hh>
 #include <seastar/core/on_internal_error.hh>
+#include "gms/gossiper.hh"
 #include "db/view/view_building_coordinator.hh"
 #include "db/view/view_build_status.hh"
 #include "locator/tablets.hh"

db/virtual_tables.cc

@@ -20,6 +20,7 @@
 #include "cdc/metadata.hh"
 #include "db/config.hh"
 #include "db/system_keyspace.hh"
+#include "query/query-result-set.hh"
 #include "db/virtual_table.hh"
 #include "partition_slice_builder.hh"
 #include "db/virtual_tables.hh"

gms/gossiper.hh

@@ -34,6 +34,7 @@
 #include "locator/token_metadata.hh"
 #include "locator/types.hh"
 #include "gms/gossip_address_map.hh"
+#include "gms/loaded_endpoint_state.hh"
 
 namespace gms {
 
@@ -71,11 +72,6 @@ struct gossip_config {
     utils::updateable_value<utils::UUID> recovery_leader;
 };
 
-struct loaded_endpoint_state {
-    gms::inet_address endpoint;
-    std::optional<locator::endpoint_dc_rack> opt_dc_rack;
-};
-
 /**
  * This module is responsible for Gossiping information for the local endpoint. This abstraction
  * maintains the list of live and dead endpoints. Periodically i.e. every 1 second this module

gms/loaded_endpoint_state.hh

@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2025-present ScyllaDB
+ */
+
+/*
+ * SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.1
+ */
+
+#pragma once
+
+#include <optional>
+
+#include "gms/inet_address.hh"
+#include "locator/types.hh"
+
+namespace gms {
+
+struct loaded_endpoint_state {
+    inet_address endpoint;
+    std::optional<locator::endpoint_dc_rack> opt_dc_rack;
+};
+
+} // namespace gms

service/storage_service.hh

@@ -15,6 +15,7 @@
 #include <seastar/core/shared_future.hh>
 #include "absl-flat_hash_map.hh"
 #include "gms/endpoint_state.hh"
+#include "gms/gossiper.hh"
 #include "gms/i_endpoint_state_change_subscriber.hh"
 #include "schema/schema_fwd.hh"
 #include "service/client_routes.hh"

tools/load_system_tablets.cc

@@ -9,6 +9,7 @@
 #include "tools/load_system_tablets.hh"
 
 #include <seastar/core/thread.hh>
+#include "query/query-result-set.hh"
 #include <seastar/util/closeable.hh>
 
 #include "locator/abstract_replication_strategy.hh"