[opencv] use filestorage to read and write eigenvectors

In their own cpp Add the following code to ：

namespace cv {
    
template <typename _Scalar, int _Dim>
class DataType<Eigen::Matrix<_Scalar, _Dim, 1>> {
    
public:
    typedef Eigen::Matrix<_Scalar, _Dim, 1> value_type;
    typedef Eigen::Matrix<typename DataType<_Scalar>::work_type, _Dim, 1> work_type;
    typedef _Scalar channel_type;
    enum {
     generic_type = 0,
        channels = _Dim,
        fmt = traits::SafeFmt<channel_type>::fmt + ((channels - 1) << 8)
    };
    typedef Vec<channel_type, channels> vec_type;
};
} //namespace cv

And then it can be like cv::Point_<T>、cv::Point3_<T> Use like that cv::FileStorage Read and write Eigne::Vector2f、Eigen::Vector3d Other types , Include related sequence types std::vector<...> and std::vector<std::vector<...>>