While Serai only needs the simple DLEq which was already present under
monero, this migrates the implementation of the cross-group DLEq I
maintain into Serai. This was to have full access to the ecosystem of
libraries built under Serai while also ensuring support for it.
The cross_group curve, which is extremely experimental, is feature
flagged off. So is the built in serialization functionality, as this
should be possible to make nostd once const generics are full featured,
yet the implemented serialization adds the additional barrier of
std::io.
It was never used as we derive entropy via the other fields in the
transcript, and explicitly add fields directly as needed for entropy.
Also drops an unused crate and corrects a bug in FROST's Schnorr
implementation which used the Group's generator, instead of the Curve's.
Also updates the Monero crate's description.
Honestly, the borrowed keys are frustrating, and this probably reduces
performance while no longer offering an order when iterating. That said,
they enable full u16 indexing and should mildly improve the API.
Cleans the Proof of Knowledge handling present in key gen.
