* Add `BaseImshowContextmanager` and `ImshowInfosContextManager` to reuse
matplotlib figure.
* Use context manager to implement `imshow_infos`
* Add unit tests.
* More general base context manager.
* unit tests for context manager.
* Improve docstring.
* Fix context manager exit cannot close figure when matplotlib>=3.4.0
* Fix unit tests
* Support inline backend in visualization.
* Imporve result visualization to support wait time and change the backend
to matplotlib.
* Add unit test for visualization
* Add adaptive dpi function
* Rename `imshow_cls_result` to `imshow_infos`.
* Support str in `imshow_infos`
* Improve docstring.