Optimized poseidon software implementation

[redshiftzero]

Currently we are using an upstream implementation of Poseidon: ark-sponge. This implementation doesn't support the optimizations suggested in the Poseidon paper (which we added the parameter generation code for in #17). We should add an implementation of Poseidon fixed-width hashing here using either code from scratch or modified ark-sponge, and add support for optimized Poseidon.

[redshiftzero]

Next steps here:

• [x] Use the crate introduced in #20 to speed up poseidon377 using the old parameters - this involves generating the optimized MDS and ARC matrices from the existing parameter set using poseidon-paramgen and hardcoding those parameters in poseidon377/params.rs. This can be backported to the oldparams branch once ready (#1102 pins the testnet folks to the oldparams branch s.t. we can do all the address breaking changes in one fell swoop).
• [x] Rebase #16 onto latest main - the plan is to merge #16 this on Monday once the latest testnet is released and folks are on oldparams.