Added missing const and ensure proper resource management with unique_ptr
Hi @sagunb Can you please review this PR ? Thank you!
Title: Add missing const and ensure proper resource management with unique_ptr

Description:

This pull request addresses two issues in the code:

1. Added missing const to the TFPackage class member functions.
   - This change improves the const-correctness of the code, ensuring that these member functions do not modify the internal state of the TFPackage objects.

2. Ensured proper resource management for the BundleReader object by using a std::unique_ptr.
   - This change ensures that the BundleReader object is correctly deallocated when the TFPackage object is destroyed, preventing potential memory leaks.

These improvements will help maintain the robustness and quality of the codebase.
