tests: add e2e tests

[ChenZiHong-Gavin]

This PR adds comprehensive end-to-end (e2e) tests for the GraphGen tool, testing different output data types and standardizing the output directory structure.

[Copilot]

Pull Request Overview

Adds comprehensive end-to-end (e2e) tests for the GraphGen tool, testing different output data types and standardizing the output directory structure.

• Creates e2e test files for atomic, aggregated, chain-of-thought, and multi-hop data generation
• Modifies output path structure to include the data type in the folder name
• Streamlines file organization by moving logs into the data directory and simplifying config file naming

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/e2e_tests/test_generate_atomic.py	E2e test for atomic data generation with proper function naming
tests/e2e_tests/test_generate_aggregated.py	E2e test for aggregated data generation
tests/e2e_tests/test_generate_cot.py	E2e test for chain-of-thought data generation with misnamed function
tests/e2e_tests/test_generate_multi_hop.py	E2e test for multi-hop data generation with misnamed function
graphgen/graphgen.py	Updates output directory structure to include data type in path
graphgen/generate.py	Reorganizes output structure and simplifies config file naming

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