accounts, core, crypto, internal: use normalised V during signature handling (#3455)

To address increasing complexity in code that handles signatures, this PR
discards all notion of "different" signature types at the library level. Both
the crypto and accounts package is reduced to only be able to produce plain
canonical secp256k1 signatures. This makes the crpyto APIs much cleaner,
simpler and harder to abuse.

accounts/abi/bind/auth.go

@@ -52,7 +52,7 @@ func NewKeyedTransactor(key *ecdsa.PrivateKey) *TransactOpts {
 			if address != keyAddr {
 				return nil, errors.New("not authorized to sign this account")
 			}
-			signature, err := crypto.SignEthereum(signer.Hash(tx).Bytes(), key)
+			signature, err := crypto.Sign(signer.Hash(tx).Bytes(), key)
 			if err != nil {
 				return nil, err
 			}