feat userver/ydb: add thread properties to config

Exposes `network-threads-num` and `client-threads-num` properties from ydb-cpp-sdk in @ref ydb::Component.
commit_hash:7a999f3b871dbf5641bbdf3952739d834752b119

Author: don-dron

ydb/src/ydb/component.yaml

@@ -64,6 +64,20 @@ properties:
                     type: boolean
                     default: true
                     description: whether to use query cache
+                network-threads-num:
+                    type: integer
+                    minimum: 1
+                    default: 2
+                    description: |
+                        Number of gRPC worker threads in YDB C++ SDK (NYdb::TDriverConfig::SetNetworkThreadsNum).
+                        Defaults to the SDK default (2).
+                client-threads-num:
+                    type: integer
+                    minimum: 0
+                    default: 0
+                    description: |
+                        Number of threads for async user callbacks in YDB C++ SDK (NYdb::TDriverConfig::SetClientThreadsNum).
+                        0 means adaptive thread pool (SDK default).
                 prefer_local_dc:
                     type: boolean
                     default: true

ydb/src/ydb/impl/config.cpp

@@ -67,6 +67,8 @@ DriverSettings ParseDriverSettings(
     auto config_database = dbconfig["database"].As<std::optional<std::string>>();
 
     result.prefer_local_dc = dbconfig["prefer_local_dc"].As<bool>(result.prefer_local_dc);
+    result.network_threads_num = dbconfig["network-threads-num"].As<std::size_t>(result.network_threads_num);
+    result.client_threads_num = dbconfig["client-threads-num"].As<std::size_t>(result.client_threads_num);
 
     result.endpoint = MergeWithSecdist(dbsecdist.endpoint, std::move(config_endpoint), dbconfig, "endpoint");
     result.database = MergeWithSecdist(dbsecdist.database, std::move(config_database), dbconfig, "database");

ydb/src/ydb/impl/config.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <chrono>
+#include <cstddef>
 #include <cstdint>
 #include <optional>
 #include <string>
@@ -40,6 +41,9 @@ struct DriverSettings {
     std::string endpoint;
     std::string database;
 
+    std::size_t network_threads_num{2};
+    std::size_t client_threads_num{0};
+
     bool prefer_local_dc{false};
     std::optional<std::string> oauth_token;
     std::optional<std::string> iam_jwt_params;

ydb/src/ydb/impl/driver.cpp

@@ -28,7 +28,9 @@ Driver::Driver(std::string dbname, impl::DriverSettings settings)
             settings.prefer_local_dc
                 ? NYdb::EBalancingPolicy::UsePreferableLocation
                 : NYdb::EBalancingPolicy::UseAllNodes
-        );
+        )
+        .SetNetworkThreadsNum(settings.network_threads_num)
+        .SetClientThreadsNum(settings.client_threads_num);
 
     if (settings.secure_connection_cert.has_value()) {
         driver_config.UseSecureConnection(*settings.secure_connection_cert);