Remove conversion of Matplotlib artifacts to Plotly objects for storage

[wk9874]

When a Matplotlib figure is stored as an artifact to the Simvue server, it is converted to a Plotly artifact and stored that way (I assume so that it can be viewed within the UI, which is very useful!). However when it is pulled back from the server using the client, the figure is returned as a Plotly object, instead of the Matplotlib figure originally stored. Can the figure be converted back to Matplotlib before being returned, so that the user gets back the same artifact which they stored?

[alahiff]

I think we should switch to storing Matplotlib plots exactly as they are, so that they can easily be returned as Matplotlib figures correctly. Transforming them to Plotly for the UI can then be done elsewhere.

[kzscisoft]

Is it worth using this:

https://plot-serializer.readthedocs.io/en/latest/getting_started.html