Define Hash + Eq for BSATN

[Centril]

Description of Changes

• Defines hash_bsatn to hash an AV encoded as BSATN.
• Defines eq_bsatn to compare AV encoded BSATN against an AV.

API and ABI breaking changes

None.

Expected complexity level and risk

2, we need to make sure the algorithms are consistent with AVs.

Testing

• proptests are provided

[kazimuth]

LGTM, everything looks clean.

I'm curious, what do the reborrows on the deserializer do? (This may have been discussed before, but if so I missed it.)

[Centril]

I'm curious, what do the reborrows on the deserializer do? (This may have been discussed before, but if so I missed it.)

Basically, they exist to make the borrow checker happy, Deserializer { reader: self.reader } is what they do, so more or less a no-op.