tests: Add fuzzing harnesses for functions parsing scripts, numbers, JSON and HD keypaths (bip32)

Summary:

Add fuzzing harnesses for DecodeRawPSBT(...), ParseHDKeypath(...),
ParseScript(...), various number parsing functions and various
JSON/univalue parsing functions.

Backport of core PR17050.

The missing corpora change is not relevant for us.

Test Plan:

ninja bitcoin-fuzzers
./test/fuzz/test_runner.py <path_to_corpus>

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D8149