consensus/clique: avoid a copy in clique (#23149)

* consensus/clique:optimize to avoid a copy in clique

* consensus/clique: test for sealhash

Co-authored-by: Martin Holst Swende <martin@swende.se>

consensus/clique/clique_test.go

@@ -112,3 +112,16 @@ func TestReimportMirroredState(t *testing.T) {
 		t.Fatalf("chain head mismatch: have %d, want %d", head, 3)
 	}
 }
+
+func TestSealHash(t *testing.T) {
+	have := SealHash(&types.Header{
+		Difficulty: new(big.Int),
+		Number:     new(big.Int),
+		Extra:      make([]byte, 32+65),
+		BaseFee:    new(big.Int),
+	})
+	want := common.HexToHash("0xbd3d1fa43fbc4c5bfcc91b179ec92e2861df3654de60468beb908ff805359e8f")
+	if have != want {
+		t.Errorf("have %x, want %x", have, want)
+	}
+}