`XOnlyPubKey` and `Taproot keys` based on quadratic residue analysis

[Sansh2356]

We need to specify what kind of pubkey there is in and how it is encoded. We don't want to use arbitrary pubkeys allowed by bitcoin which have a large variation in their DER encoding and ECDSA/Schnorr usage. We would like to use as mentioned by @mcelrath taproot-style pubkeys encoded in 64 bits using the quadratic residue algorithm. The point of this pubkey is that it will be used for signatures on the UnCommittedMetadata and for ECIES encryption between mining nodes.

Investigate the compatibility of Taproot keys with ECIES.