Add poseidon reference implementation (using sage)

[tsunrise]

After #57 is merged, we might consider adding some sage scripts as a reference implementation to make sure the implementation is correct.

Originally posted by @BoyuanFeng in #57 (comment)

[SupremoUGH]

Closed. Poseidon consists of multiple rounds, split into full and partial rounds. The hardcoded test for those (albeit not generated by a sage script) is done in constants.rs in

• Feature: Parameter Generation for Poseidon Hash #57

Each round consists of three steps, namely:

• Add round constants, whose hardcoded values test given by parameters_hardcoded_test/lfsr_values is done in Move Poseidon sage script #206
• Permutation, whose test given by permutation_hardcoded_test/width3 is done in Deprecate Old Poseidon Hash #168
• MDS Matrices, whose test given by mds_hardcoded_tests/width*n* is done in feat: add poseidon encryption implementation #149.