refactor: Replace std::bind with lambdas

Lambdas are shorter and more readable.
Changes are limited to std::thread ctor calls only.

src/index/base.cpp

@@ -349,8 +349,7 @@ void BaseIndex::Start()
         return;
     }
 
-    m_thread_sync = std::thread(&util::TraceThread, GetName(),
-                                std::bind(&BaseIndex::ThreadSync, this));
+    m_thread_sync = std::thread(&util::TraceThread, GetName(), [this] { ThreadSync(); });
 }
 
 void BaseIndex::Stop()