* fuzz: Add honggfuzz
- Added honggfuzz in fuzz2/ (alongside libfuzzer in fuzz/)
- Created convenience script for fuzzing binary decoder
- Created a script to convert inputs that cause crashes into arrays so
that they can be used in unit tests
* Create honggfuzz as subdirectory of fuzz/
- Reorg so that honggfuzz is under fuzz/ instead of in a separate
sibling-level directory fuzz2
- Update fuzz/README.md to make it explicit that it covers libfuzzer
Note: `cargo fuzz`/libfuzzer seems to insist that its folder exists at
`$REPO/fuzz/` so that's the reason for this particular folder structure.
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Co-authored-by: y <y>
