Add fallback command-line mode for orca image export

[jonmmease]

The plotly.io.write_image/to_image functions start an orca server and send image export requests to the orca server over a local port. This provides the best performance for repeated image export requests, but at times folks have had trouble with this local server connection. See

• Orca.exe hangs on write_image, freezes up and I have to kill the process. #1460
• Directly save image (without opening in browser) #880 (comment)

It would be useful to provide to option to call orca in command-line mode. This would involve writing the figure to a temporary file, calling orca graph on the file to create a temporary image file, then reading the image file bytes into memory, and deleting both temporary files. This would be quite a bit slower (1-2 seconds per image), but it would likely be more reliable for some environments since it does not require communication over a local port.

The API should be designed along with #1570.

[gvwilson]

Hi - we are currently trying to tidy up Plotly's public repositories to help us focus our efforts on things that will help users most. Since this issue has been sitting for several years, I'm going to close it. If it's still a concern, we'd be grateful if you could open a new issue (with a short reproducible example if appropriate) so that we can add it to our backlog. Thanks for your help - @gvwilson