bug redis: disconnect slots on stop in topology holder

`ClusterTopologyHolder::Stop()` was not disconnecting the slots, resulting in new events apearing after the `Stop()`:
```
/home/runner/work/userver/userver/redis/src/storages/redis/impl/cluster_sentinel_impl.cpp:884:13: runtime error: member access within address 0x51100001e040 which does not point to an object of type 'userver_ns::storages::redis::impl::ClusterSentinelImpl'
 0x51100001e040: note: object has invalid vptr
  04 00 00 00  fb 42 00 00 03 00 00 00  d0 7d 01 00 30 51 00 00  80 39 06 00 60 51 00 00  00 00 00 00
               ^~~~~~~
               invalid vptr
#0 0x5561b8eb5ae5 in userver_ns::v1::storages::redis::impl::ClusterSentinelImpl::Init()::$_0::operator()(std::string, userver_ns::v1::storages::redis::RedisState) const /userver/redis/src/storages/redis/impl/cluster_sentinel_impl.cpp:884:13
```

Tests: протестировано CI
commit_hash:52161d57a664620907e07767dcd8525d75081b4c

Author: apolukhin

redis/functional_tests/cluster_auto_topology_pubsub/tests/test_redis_pubsub.py

@@ -2,10 +2,8 @@
 
 import redis
 
-# Some messages may be lost (it's a Redis limitation)
-REDIS_PORT = 6379
-REQUESTS_RETRIES = 42
-REQUESTS_RETRIES_NOT_EXPECTED = 3
+# Some messages may be lost (it's a Redis limitation). *_failover tests require more than 100 retries on slow CI
+REQUESTS_RETRIES = 9000
 REQUESTS_RELAX_TIME = 1.0
 
 # Target channel. Same constant in c++ code
@@ -89,8 +87,7 @@ async def _test_service_sharded_subscription(
 
 async def _validate_service_publish(service_client, nodes, shards_count=0):
     """
-    Check publishing by service with 'publish' command in each shard is heard
-    from any node from any shard
+    Check publishing by service with 'publish' command in each shard is heard from any node from any shard
     """
     redis_clients = [(node, node.get_client()) for node in nodes]
 
@@ -325,8 +322,7 @@ async def test_cluster_happy_path(service_client, redis_cluster_topology):
 
 async def test_cluster_add_shard(service_client, redis_cluster_topology):
     """
-    Check service still can receive messages published on any of cluster's node
-    even after addition of new shard
+    Check service still can receive messages published on any of cluster's node even after addition of new shard
     """
 
     await service_client.delete('/redis-cluster')

redis/src/storages/redis/impl/cluster_sentinel_impl.cpp

@@ -282,6 +282,9 @@ class ClusterTopologyHolder final : public TopologyHolderBase,
     }
 
     void Stop() override {
+        signal_node_state_change_.disconnect_all_slots();
+        signal_topology_changed_.disconnect_all_slots();
+
         ev_thread_.RunInEvLoopBlocking([this] {
             update_topology_timer_.Stop();
             explore_nodes_timer_.Stop();
@@ -433,7 +436,6 @@ class ClusterTopologyHolder final : public TopologyHolderBase,
     bool IsInitialized() const { return is_nodes_received_.load() && is_topology_received_.load(); }
     ///}
 
-    // NOLINTNEXTLINE(misc-non-private-member-variables-in-classes)
     boost::signals2::signal<void(HostPort, Redis::State)> signal_node_state_change_;
     boost::signals2::signal<void(size_t shards_count)> signal_topology_changed_;
     NodesStorage nodes_;