add new crate chia-bls

[arvidn]

with support for all Chia key operations, from BIP39, hardened and unhardened key derivation, signatures, aggregation and verification.

The overview of the functions added in this crate, see the README.

The unit tests include some regression tests against blspy, with manual python code snippets.

There are two fuzz targets, one that loads blspy and validates results against it (here) and one that checks internal consistency of these functions (here). e.g. unhardened derivation of secret key and public key independently still validate the signature.

There are 3 benchmark targets. This implementation takes about 2.3 times longer to verify a signature compared to blspy/bls-signatures.

     Running benches/verify.rs
verify, small msg       time:   [2.3635 ms 2.3666 ms 2.3706 ms]
                        change: [-0.2317% -0.0294% +0.1766%] (p = 0.80 > 0.05)
                        No change in performance detected.
Found 10 outliers among 100 measurements (10.00%)
  2 (2.00%) high mild
  8 (8.00%) high severe

verify, 4kiB msg        time:   [2.3765 ms 2.3797 ms 2.3838 ms]
                        change: [-0.5150% -0.2241% +0.0461%] (p = 0.12 > 0.05)
                        No change in performance detected.
Found 14 outliers among 100 measurements (14.00%)
  3 (3.00%) high mild
  11 (11.00%) high severe