perf(common): 批量复制 RawMessage，优化请求深拷贝 (#7221)

* perf(relay): bulk-copy Responses raw JSON fields

* perf(common): share RawMessage deep-copy optimization

---------

Co-authored-by: CaIon <i@caion.me>

common/copy.go

 package common
 
 import (
+	"bytes"
+	"encoding/json"
 	"fmt"
 
 	"github.com/jinzhu/copier"
@@ -11,7 +13,18 @@ func DeepCopy[T any](src *T) (*T, error) {
 		return nil, fmt.Errorf("copy source cannot be nil")
 	}
 	var dst T
-	err := copier.CopyWithOption(&dst, src, copier.Option{DeepCopy: true, IgnoreEmpty: true})
+	err := copier.CopyWithOption(&dst, src, copier.Option{
+		DeepCopy: true, IgnoreEmpty: true,
+		Converters: []copier.TypeConverter{{
+			SrcType: json.RawMessage{},
+			DstType: json.RawMessage{},
+			Fn: func(src any) (any, error) {
+				// Copy raw JSON in bulk while retaining independent storage for
+				// request mutation and retries, instead of reflecting over each byte.
+				return json.RawMessage(bytes.Clone(src.(json.RawMessage))), nil
+			},
+		}},
+	})
 	if err != nil {
 		return nil, err
 	}