disttask: add StepExecFrameworkInfo as an example of Impl access Base (#52192)

ref pingcap/tidb#47006

br/pkg/mock/storage/storage.go

@@ -5,6 +5,7 @@
 //
 //	mockgen -package mockstorage github.com/pingcap/tidb/br/pkg/storage ExternalStorage
 //
+
 // Package mockstorage is a generated GoMock package.
 package mockstorage
 
@@ -39,6 +40,11 @@ func (m *MockExternalStorage) EXPECT() *MockExternalStorageMockRecorder {
 	return m.recorder
 }
 
+// ISGOMOCK indicates that this struct is a gomock mock.
+func (m *MockExternalStorage) ISGOMOCK() struct{} {
+	return struct{}{}
+}
+
 // Close mocks base method.
 func (m *MockExternalStorage) Close() {
 	m.ctrl.T.Helper()