crypto: replace ToECDSAPub with error-checking func UnmarshalPubkey (#16932)

ToECDSAPub was unsafe because it returned a non-nil key with nil X, Y in
case of invalid input. This change replaces ToECDSAPub with
UnmarshalPubkey across the codebase.

signer/core/api.go

@@ -432,13 +432,11 @@ func (api *SignerAPI) EcRecover(ctx context.Context, data, sig hexutil.Bytes) (c
 	}
 	sig[64] -= 27 // Transform yellow paper V from 27/28 to 0/1
 	hash, _ := SignHash(data)
-	rpk, err := crypto.Ecrecover(hash, sig)
+	rpk, err := crypto.SigToPub(hash, sig)
 	if err != nil {
 		return common.Address{}, err
 	}
-	pubKey := crypto.ToECDSAPub(rpk)
-	recoveredAddr := crypto.PubkeyToAddress(*pubKey)
-	return recoveredAddr, nil
+	return crypto.PubkeyToAddress(*rpk), nil
 }
 
 // SignHash is a helper function that calculates a hash for the given message that can be