Refactor VirtualFile memory management and enhance robustness - #71

- Correctly handle memory allocation in oslReadEntireFileToMemory:
- Standardize memory block handling with BLOCK_SIZE macro for consistent allocation.
- Enhance error handling throughout the VirtualFile functions to ensure proper memory cleanup.
- Add comments for clarity and consistency in error handling and memory allocation logic.
- Ensure safe buffer management in functions like vfsMemGets to prevent buffer overflows.