49f4c7f0699e5e19ac6e41ef5b607392dd7a2983 tests: Add fuzzing harness for various PSBT related functions (practicalswift)
Pull request description:
Add fuzzing harness for various PSBT related functions.
**Testing this PR**
Run:
```
$ CC=clang CXX=clang++ ./configure --enable-fuzz \
--with-sanitizers=address,fuzzer,undefined
$ make
$ src/test/fuzz/psbt
```
ACKs for top commit:
MarcoFalke:
re-ACK 49f4c7f0699e5e19ac6e41ef5b607392dd7a2983 🐟
Tree-SHA512: 4cebe62bd8c244ee40a43e829f5bd175ab40e1dfbbab1affb1529374858225820d6c9fa9ba45862bf56c1522845422fd96d620cedbdec52a67ac1449dec4e1b2