[bls-signatures] Add support verifying signatures and pop directly as byte arrays

[samkim-crypto]

Problem

For places like the vote program anza-xyz/agave#9310, public keys are stored as raw bytes rather than as Pubkey or PubkeyCompressed types provided from the solana-bls-signatures crate. It would be nice if the crate public interface supports verifying signatures or PoPs by directly interpreting the input from raw bytes.

Summary of Changes

Updated the verification functions so that it can interpret public keys, signatures, or PoPs directly from byte arrays. It was pretty simple to do this since we can just implement the AsPubkey, AsSignature, and AsProofOfPossession traits for the fixed size byte arrays.

[zz-sol]

LGTM!