Implement the Mastic VDAF

[cjpatton]

Mastic is a new VDAF (https://github.com/jimouris/draft-mouris-cfrg-mastic) designed as a replacement for Poplar1 that is more efficient and provides more functionality. It is comprised of two components:

1. FLP, as in the flp module
2. VIDPF, an extension of IDPF (the idpf module) that still needs to be implemented

Security analysis for Mastic is underway (https://eprint.iacr.org/2024/221), but is incomplete as of this writing. We're confident in the composition of FLP and VIDPF, but the parameters for each are subject to change. In the meantime, it should be considered experimental and only made available via the "experimental" feature. Likewise, we should not deprecate Poplar1 until Mastic is finished and we have high confidence in its security.

[cjpatton]

Right now the plan is for @armfazh to implement VIDPF (already underway, see #933), then have @hannahdaviscrypto implement the end-to-end protocol.