Use bump allocator for DB mutations

[Jake-Shadle]

Right now we are using the global heap for building the SQL queries for mutations, but this is extremely wasteful since it's all strings that only need to last until they are executed before being dropped. I've mitigated this somewhat by presizing strings in most cases, but not all, a much better solution is to just use a bump allocator (eg. bumpalo) for the whole receive request -> deserialize -> build SQL queries -> execute -> send response chain as a majority of the heap allocations involved in that process are dropped immediately, and are not data that has any special Drop behavior.

This is definitely not needed right now, but wanted to write down this idea so I don't forget.