fix: make every flakey test write to its own files

[MegaRedHand]

This PR fixes our flakey tests by making each test that writes to the filesystem do it to files not read or written to in other tests.

All flakey tests seem to be gone when running this script:

#!/usr/bin/env bash

set -e
cd contracts
forge build

for i in {1..100} ; do
    forge test
done