Currently spectest fuzzing indexes into a compile-time-created array of
strings which is the list of input files, but the order of this array is
dependent on the filesystem that we're reading from. This means that
inputs from oss-fuzz may not be easily reproducible locally because
files could be read in different orders, so indexes could be distinct.
This commit instead reads the directory paths, then sorts them, then
includes them for testing. That way fuzz inputs at a specific commit
should be consistent.
* Add a spec test fuzzer for Config
This commit adds a new fuzzer which is intended to run on oss-fuzz. This
fuzzer creates and arbitrary `Config` which *should* pass spec tests and
then asserts that it does so. The goal here is to weed out any
accidental bugs in global configuration which could cause
non-spec-compliant behavior.
* Move implementation to `fuzzing` crate
