Integrate GraphRAG-LLM package into the codebase

[gaudyb]

Integrate the GraphRAG-LLM package into the microsoft/benchmark-qed codebase. Refactor and clean up the local implementation by replacing redundant code with the standardized functionality already implemented in the GraphRAG-LLM library.

Task details:

• Identify all local code that duplicates or can be replaced by the corresponding components in GraphRAG-LLM.
• Remove redundant, overlapping, or obsolete local code.
• Refactor code where necessary to ensure seamless integration and interoperability with GraphRAG-LLM.
• Ensure that all related tests pass and that overall functionality remains stable.
• Update documentation to reflect any interfaces or usage changes.

Acceptance Criteria:

• All relevant local code has been replaced by GraphRAG-LLM package functionality.
• No loss in current features or stability.
• Codebase is cleaner and easier to maintain.
• All builds/tests complete successfully.