Arena memory support?

[elcritch]

> This is a standalone threadsafe memory pool. The block size is fixed at 
> compile-time:

Thanks! I was reading through that. It looks like it's solving a similar type 
of problem. Not sure if it could be tweaked for my use case. The comments 
mention it being for cross-thread uses and it looks to use atomics to keep 
track of the index pointer?
    
    
    MemBlock {.union.} = object
        next: Atomic[pointer]
        ...
    
    
    Run