Look into zero heap for embedded applications

[stephenberry]

Likely have to rework error handling to avoid exceptions in this context.

[mwalcott3]

Also, static thread_local std::string temp buffers will need to get replaced. We could do this fairly easily if a max key size was supplied as a compile-time option. Perhaps there is an even better solution. I'm not very familiar with embedded programming patterns/solutions.

[stephenberry]

I did update the code so that the static thread_local std::string is only needed for non-contiguous buffers or keys with escapes. So, in an embedded context a contiguous buffer can be used and we just wouldn't allow keys with escaped characters.

[stephenberry]

We are continuing to move towards using the heap only when necessary. We are using glaze on embedded platforms and will continue to improve its embedded support. Closing this now since we are intending to only allocate where needed and continuing to make progress.