Revert vendor directory to support old golang (GOPATH mode)

gomodule is still in progress to migrate for now, hence multus
team decide to keep vendor directory to support build without
gomodule.

vendor/github.com/modern-go/reflect2/unsafe_struct.go

@@ -0,0 +1,59 @@
+package reflect2
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+type UnsafeStructType struct {
+	unsafeType
+	likePtr bool
+}
+
+func newUnsafeStructType(cfg *frozenConfig, type1 reflect.Type) *UnsafeStructType {
+	return &UnsafeStructType{
+		unsafeType: *newUnsafeType(cfg, type1),
+		likePtr:    likePtrType(type1),
+	}
+}
+
+func (type2 *UnsafeStructType) LikePtr() bool {
+	return type2.likePtr
+}
+
+func (type2 *UnsafeStructType) Indirect(obj interface{}) interface{} {
+	objEFace := unpackEFace(obj)
+	assertType("Type.Indirect argument 1", type2.ptrRType, objEFace.rtype)
+	return type2.UnsafeIndirect(objEFace.data)
+}
+
+func (type2 *UnsafeStructType) UnsafeIndirect(ptr unsafe.Pointer) interface{} {
+	if type2.likePtr {
+		return packEFace(type2.rtype, *(*unsafe.Pointer)(ptr))
+	}
+	return packEFace(type2.rtype, ptr)
+}
+
+func (type2 *UnsafeStructType) FieldByName(name string) StructField {
+	structField, found := type2.Type.FieldByName(name)
+	if !found {
+		return nil
+	}
+	return newUnsafeStructField(type2, structField)
+}
+
+func (type2 *UnsafeStructType) Field(i int) StructField {
+	return newUnsafeStructField(type2, type2.Type.Field(i))
+}
+
+func (type2 *UnsafeStructType) FieldByIndex(index []int) StructField {
+	return newUnsafeStructField(type2, type2.Type.FieldByIndex(index))
+}
+
+func (type2 *UnsafeStructType) FieldByNameFunc(match func(string) bool) StructField {
+	structField, found := type2.Type.FieldByNameFunc(match)
+	if !found {
+		panic("field match condition not found in " + type2.Type.String())
+	}
+	return newUnsafeStructField(type2, structField)
+}