Added referened and Optimize and Refactor Microgrid Test and Utility Code for Improved Clarity and Reusability

[Mattral]

Description:
This PR introduces optimizations and refactoring across two files to improve code readability, reusability, and maintainability without changing existing functionality. The modifications are focused on enhancing clarity and aligning with best practices.

Summary of Changes:

1. Microgrid Modular Setup Code:

   • Simplified parameter handling, including safe copying of default values and use of explicit defaults to prevent unintended side effects.
   • Converted default_params to uppercase DEFAULT_PARAMS to clearly indicate its status as a constant, following Python conventions.
   • Leveraged conditional expressions (or operator) to streamline default assignments, making code more concise.

2. MPC Test Suite:

   • Implemented a setUp method to centralize shared constants (e.g., max_steps, pv_const, load_const) and reusable time series data, reducing repetition across tests.
   • Added a helper method create_microgrid to construct customized microgrid setups, improving test readability and reducing setup complexity.
   • Refactored assertions by calculating reusable values, making tests more concise and easier to understand.
   • Consolidated module imports within the class to enhance consistency and readability across test methods.

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📚 Documentation preview 📚: https://pymgrid--255.org.readthedocs.build/en/255/