Text formatted values except bytea can be directly scanned to []byte

This significantly improves performance of scanning text to []byte as it
avoids multiple allocations and copies.

pgtype.go

@@ -779,7 +779,7 @@ func (ci *ConnInfo) PlanScan(oid uint32, formatCode int16, dst interface{}) Scan
 			}
 		case *[]byte:
 			switch oid {
-			case ByteaOID, TextOID, VarcharOID:
+			case ByteaOID, TextOID, VarcharOID, JSONOID:
 				return scanPlanBinaryBytes{}
 			}
 		case BinaryDecoder:
@@ -789,6 +789,10 @@ func (ci *ConnInfo) PlanScan(oid uint32, formatCode int16, dst interface{}) Scan
 		switch dst.(type) {
 		case *string:
 			return scanPlanString{}
+		case *[]byte:
+			if oid != ByteaOID {
+				return scanPlanBinaryBytes{}
+			}
 		case TextDecoder:
 			return scanPlanDstTextDecoder{}
 		}

pgtype_test.go

@@ -79,6 +79,14 @@ func TestConnInfoScanTextFormatInterfacePtr(t *testing.T) {
 	assert.Equal(t, "foo", got)
 }
 
+func TestConnInfoScanTextFormatNonByteaIntoByteSlice(t *testing.T) {
+	ci := pgtype.NewConnInfo()
+	var got []byte
+	err := ci.Scan(pgtype.JSONBOID, pgx.TextFormatCode, []byte("{}"), &got)
+	require.NoError(t, err)
+	assert.Equal(t, []byte("{}"), got)
+}
+
 func TestConnInfoScanBinaryFormatInterfacePtr(t *testing.T) {
 	ci := pgtype.NewConnInfo()
 	var got interface{}