Import Poseidon hash into Zebra

[dconnolly]

As defined in NU5 spec:
https://zips.z.cash/protocol/nu5.pdf#poseidonhash

For reference, one implementation is over in the orchard crate: https://github.com/zcash/orchard/blob/main/src/primitives/poseidon.rs

Scheduling

This is only required for the wallet work, because it's used to create nullifiers.

[teor2345]

I moved this task to sprint 13 because the anchors are a higher priority - they are blocking the history chain contextual validation and testing.

[teor2345]

We decided to favour importing cryptography over re-implementing it, at least until after NU5 activation.

[teor2345]

We're not planning to do full-node wallet work any time soon.

If we do, we'll need to decide if this ticket is in scope, and update its content, because the spec has changed since it was created.