Adding modular heap support to RTEMS

This project aims to update the current memory allocator used by RTEMS to be modular, allowing users to provide their own heap implementation or use one supplied by RTEMS. It will also include implementing the TLSF allocator as the default allocator instead of the current first-fit approach. This change will address the existing fragmentation and unpredictable runtime issues associated with the current allocator. Additionally, the project will explore the implementation of RT-Mimalloc, a modified version of Microsoft’s mimalloc optimized for real-time systems, representing the first open-source realization of this allocator. Finally, the project will add an allocator benchmark to evaluate the new memory allocators as well as any user-provided implementations.