add hex, endian, multi-exp and hash methods

[mikelodder7]

This PR implements the elliptic-curve interfaces for hash to curve and removes the code duplication that existed from the hash_to_curve folder. This required updating the MRV to 1.66. Currently can't implement all of the elliptic-curve/hash2curve traits but most of them are.

• Added are endianess for hex and bytes.
• Removed the alloc requirement for pairing
• implemented LowerHex and UpperHex
• Makes ZERO and ONE to match RustCrypto crates like k256 and p256

[mikelodder7]

Side note: with this PR and one more to come then I can remove the need for the bls12_381_plus fork.