Adding the hvplot backend

[asewnath]

Description

This PR expands upon the hvplot backend introduced in #158. All other diagnostic types are reformatted to have a base class and child classes for each backend. Each base class includes two methods: data_prep and configure_plot. configure_plot is a virtual method that is resolved once a child class for either emcpy or hvplot is instantiated.

figure_driver is updated to reflect these changes

[asewnath]

Moving github action fix to a different PR since it's still not resolved

[CoryMartin-NOAA]

Very cool, thanks!

[EdwardSafford-NOAA]

Changes look good, just had the one question on the documentation in the Emcpy* classes.

[danholdaway]

Thanks Akira. It's great to have a complete backend utilizing hvplot. For future reference you should use git mv to rename files so their history is preserved. I'm concerned that the codes aren't tested and so the interfaces could get broken. Do you plan to add some testing through the notebook style of testing?

[asewnath]

Thanks Akira. It's great to have a complete backend utilizing hvplot. For future reference you should use git mv to rename files so their history is preserved. I'm concerned that the codes aren't tested and so the interfaces could get broken. Do you plan to add some testing through the notebook style of testing?

Hi Dan, thanks for the comment. I'll add hvplot testing in another PR