Replace raw new[] with std::vector for RAII memory management

[atta-ullah01]

Summary of Changes

Replaced raw pointer arrays allocated with new[] and released with delete[] by std::vector in Subdivision_method_3 and Matrix_search.

This transition to RAII (Resource Acquisition Is Initialization) ensures automatic memory management and exception safety for temporary buffers used in:

• Subdivision_method_3: PQQ_1step, PTQ_1step, DQQ_1step, and Sqrt3_1step internal host implementations.
• Matrix_search: monotone_matrix_search implementation.

Logic using pointer arithmetic was preserved by utilizing std::vector::data().

Release Management

• Affected package(s): Subdivision_method_3, Matrix_search
• Issue(s) solved (if any):
• Feature/Small Feature (if any):
• Link to compiled documentation (obligatory for small feature):
• License and copyright ownership: I confirm that I have the right to contribute these changes.

[lrineau]

Thanks for the contribution.

[sloriot]

Successfully tested in CGAL-6.2-Ic-82