feat: implement UncompressedEncoding

The uncompressed representation (both coordinates are present in an affine point's representation) is useful in cases where one would want to avoid paying for the cost of a point decompression (e.g. public parameter caching).

Implement uncompressed encoding for affine representations,
Update Rust toolchain to version 1.60.0 to satisfy the requirements of constant_time_eq & regex,
Add paste dependency at version 1.0.12 in order to give a specific struct for that representation for each of Pallas, Vesta through a macro.
Implement serialization / deserialization for the uncompressed encoding, and test it.

Use case: Point (de)serialization when caching public parameters (for e.g. a vector Pedersen commitments), where the deserialization can be prohibitively expensive if done with the compressed form of the points. The uncompressed points do not have that flaw.

zcash / pasta_curves

feat: implement UncompressedEncoding #73