add Poseidon implementation over bn254

[HSG88]

Description

This PR adds support for Poseidon hash over the scalar field of BN254, Poseidon has better performance compared to MiMC and is being used in multiple projects.

Fixes #494

Type of change

• [*] New feature (non-breaking change which adds functionality)
• [*] This change requires a documentation update

How has this been tested?

All unit tests have been made according to the code referenced in Poseidon paper page 20 footnote 16.

How has this been benchmarked?

The code hasn't been benchmarked yet.

Checklist:

• [*] I have performed a self-review of my code
• [*] I have commented my code, particularly in hard-to-understand areas
• [*] New and existing unit tests pass locally with my changes

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

:white_check_mark: HSG88
:x: lightning-li
_{You have signed the CLA already but the status is still pending? Let us recheck it.}