Allow switching between MPI and srun as backends

[jan-janssen]

Summary by CodeRabbit

• New Features
  • Introduced an optional parameter use_srun to enhance control over task execution in simulation environments. This allows users to optionally utilize srun for launching simulations, providing flexibility in resource management and execution strategies.
• Enhancements
  • Expanded functionality across multiple modules to support the new use_srun parameter, ensuring consistent behavior and integration in different contexts of the application.