fix: Replace first_run static bool with class variable

Fix of this issue #63 (closed)

engine/include/OpenScenarioEngine/OpenScenarioEngine.h

 /********************************************************************************
- * Copyright (c) 2021-2024 Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
+ * Copyright (c) 2021-2025 Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
  * Copyright (c) 2022-2023 Ansys, Inc.
  *
  * This program and the accompanying materials are made available under the
@@ -184,6 +184,7 @@ private:
   ScenarioDefinitionPtr scenario_definition_ptr_{nullptr};
 
   bool finished_{false};
+  bool first_run_{true};
 
   std::optional<unsigned int> random_seed_value_override_{std::nullopt};
 };