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_iface.go

@@ -0,0 +1,64 @@
+package reflect2
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+type iface struct {
+	itab *itab
+	data unsafe.Pointer
+}
+
+type itab struct {
+	ignore unsafe.Pointer
+	rtype  unsafe.Pointer
+}
+
+func IFaceToEFace(ptr unsafe.Pointer) interface{} {
+	iface := (*iface)(ptr)
+	if iface.itab == nil {
+		return nil
+	}
+	return packEFace(iface.itab.rtype, iface.data)
+}
+
+type UnsafeIFaceType struct {
+	unsafeType
+}
+
+func newUnsafeIFaceType(cfg *frozenConfig, type1 reflect.Type) *UnsafeIFaceType {
+	return &UnsafeIFaceType{
+		unsafeType: *newUnsafeType(cfg, type1),
+	}
+}
+
+func (type2 *UnsafeIFaceType) Indirect(obj interface{}) interface{} {
+	objEFace := unpackEFace(obj)
+	assertType("Type.Indirect argument 1", type2.ptrRType, objEFace.rtype)
+	return type2.UnsafeIndirect(objEFace.data)
+}
+
+func (type2 *UnsafeIFaceType) UnsafeIndirect(ptr unsafe.Pointer) interface{} {
+	return IFaceToEFace(ptr)
+}
+
+func (type2 *UnsafeIFaceType) IsNil(obj interface{}) bool {
+	if obj == nil {
+		return true
+	}
+	objEFace := unpackEFace(obj)
+	assertType("Type.IsNil argument 1", type2.ptrRType, objEFace.rtype)
+	return type2.UnsafeIsNil(objEFace.data)
+}
+
+func (type2 *UnsafeIFaceType) UnsafeIsNil(ptr unsafe.Pointer) bool {
+	if ptr == nil {
+		return true
+	}
+	iface := (*iface)(ptr)
+	if iface.itab == nil {
+		return true
+	}
+	return false
+}