Phase 3: Gradually Move C/C++ Files to New Location

[Sinitca-Aleksandr]

This issue tracks the third phase of our C/C++ code migration plan. The goal is to gradually move C/C++ files from their current locations to the new organized structure while maintaining full backward compatibility.

Objectives:

1. Create cpp subdirectory in StatTools/
2. Move C/C++ source files to new location
3. Update build system to find files in new location
4. Maintain both old and new import paths during transition
5. Verify all functionality remains intact

Implementation Plan:

1. Create StatTools/cpp/ directory structure:

   StatTools/
   ├── cpp/
   │   ├── StatTools_C_API.cpp
   │   └── DFA.cpp
   └── ... (other files)
   

2. Update CMakeLists.txt to reference new file locations
3. Modify setup.py build configuration for new structure
4. Create symlinks or copy files temporarily if needed for compatibility
5. Add comprehensive tests for both old and new file locations
6. Document the file migration in CHANGELOG.md

Acceptance Criteria:

• All C/C++ files successfully moved to cpp/ subdirectory
• Build system correctly finds files in new location
• Both old and new import paths continue to work
• No performance degradation from file relocation
• Tests pass for all functionality
• Migration documented with clear timeline