Refactor: Refactor KEDF management in ESolver_OF

[sunliang98]

• Introduced KEDF_Manager class to encapsulate KEDF functionalities, replacing individual KEDF instances (TF, VW, WT, LKT, ML) in ESolver_OF.
• Updated ESolver_OF to initialize and utilize KEDF_Manager for potential, energy, energy density, and stress calculations.

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