[Refactor] Restructure ParaCOSM/CSM directory organization

[HaibinLai]

📝 Description

We need to reorganize the directory structure of the ParaCOSM/CSM module to make it more maintainable, clearer, and easier for contributors and users to navigate.

🎯 Objectives

ParaCOSM/
├── core/              # main scheduling 
├── graph_storage/     # storage layer
├── interfaces/        # definitions of public interfaces, API endpoints
├── executor/          # all the CSM algorithm 
├── utils/             # helper functions, common utilities
├── tests/             # unit & integration tests for CSM
│     └── ...
├── examples/          # example usage or sample configs. also merge some bash scripts into this place
└── Readme.md

Considerations / Risks

Need to ensure no circular imports introduced after restructuring.
Keep backward compatibility if there are external users depending on path structure (if applicable).

[HaibinLai]

The matching executor should be updated first. Some of the bugs can also be issued here