core/types: change parameter order of SignAuth and rename

The signing key should be passed first, because it is usually in a variable,
while the authorization will often be a literal.

Compare

    a, err := types.SignAuthorization(types.SetCodeAuthorization{
        ChainID: getChainID(),
        Nonce: getNonce(),
    }, key)

with

    a, err := types.SignAuthorization(key, types.SetCodeAuthorization{
        ChainID: getChainID(),
        Nonce: getNonce(),
    })

core/blockchain_test.go

@@ -4273,16 +4273,16 @@ func TestEIP7702(t *testing.T) {
 	// 1. tx -> addr1 which is delegated to 0xaaaa
 	// 2. addr1:0xaaaa calls into addr2:0xbbbb
 	// 3. addr2:0xbbbb  writes to storage
-	auth1, _ := types.SignAuth(types.SetCodeAuthorization{
+	auth1, _ := types.SignAuthorization(key1, types.SetCodeAuthorization{
 		ChainID: gspec.Config.ChainID.Uint64(),
 		Address: aa,
 		Nonce:   1,
-	}, key1)
+	})
-	auth2, _ := types.SignAuth(types.SetCodeAuthorization{
+	auth2, _ := types.SignAuthorization(key2, types.SetCodeAuthorization{
 		ChainID: 0,
 		Address: bb,
 		Nonce:   0,
-	}, key2)
+	})
 
 	_, blocks, _ := GenerateChainWithGenesis(gspec, engine, 1, func(i int, b *BlockGen) {
 		b.SetCoinbase(aa)

core/types/tx_setcode.go

@@ -87,28 +87,22 @@ type authorizationMarshaling struct {
 	S       hexutil.U256
 }
 
-// SignAuth signs the provided authorization.
+// SignAuthorization sets the signature of a code authorization.
-func SignAuth(auth SetCodeAuthorization, prv *ecdsa.PrivateKey) (SetCodeAuthorization, error) {
+func SignAuthorization(prv *ecdsa.PrivateKey, auth SetCodeAuthorization) (SetCodeAuthorization, error) {
 	sighash := auth.sigHash()
 	sig, err := crypto.Sign(sighash[:], prv)
 	if err != nil {
 		return SetCodeAuthorization{}, err
 	}
-	return auth.withSignature(sig), nil
-}
-
-// withSignature updates the signature of an Authorization to be equal the
-// decoded signature provided in sig.
-func (a *SetCodeAuthorization) withSignature(sig []byte) SetCodeAuthorization {
 	r, s, _ := decodeSignature(sig)
 	return SetCodeAuthorization{
-		ChainID: a.ChainID,
+		ChainID: auth.ChainID,
-		Address: a.Address,
+		Address: auth.Address,
-		Nonce:   a.Nonce,
+		Nonce:   auth.Nonce,
 		V:       sig[64],
 		R:       *uint256.MustFromBig(r),
 		S:       *uint256.MustFromBig(s),
-	}
+	}, nil
 }
 
 func (a *SetCodeAuthorization) sigHash() common.Hash {