Custom Memory Allocator

[ShikenNuggets]

Currently the engine uses C++'s standard memory allocation. Ideally we would use a custom allocator. Some boilerplate has been written for a few allocators (see the Memory folder), but implementing the final "main" allocator and integration work is needed.

The custom memory allocator should:

• Allocate large blocks of memory upfront to improve performance
• Provide debugging capabilities to help prevent leaks/corruption
• Track memory usage from different engine subsystems and impose a memory budget
• Defragmentation

[ShikenNuggets]

Still on my radar, but deprioritized for now as memory allocation performance is not a major concern at the moment.