Problem: persisting keys in binary script form is bad for traversing

[yrashk]

Right now, both keys and values are persisted with their size prefixes (according to the binary form data representation rules). This motivation for this was to avoid allocating memory to put a prefix in front of them upon retrieval.

However, when traversing a range of keys (CURSOR/SEEK and then /NEXT), it'll trip up the cursor when a "composite key" size changes, changing the very beginning of it.

Proposed solution: make Env stack store references to data without their size prefixes (as slices already have length) and hence we can move to persisting data as is in the database. Having stack that was is not big of a deal because we can write size prefixes on demand when we are sending data back, avoiding allocations there.