Update image rotator for Matplotlib 3.8

[QuLogic]

This also updates the generator to handle the move of gallery files.

This adds ecdf, stackplot, and stairs, and removes step. A lot of images changed with no reason, so I'm looking to see if there's a way to make the plots more reproducible.

Fixes #88

[QuLogic]

Also, the generator doesn't include 3d and unstructured; should we add those in?

[story645]

I think 3D definitely, unstructured is more 🤷‍♀️ b/c all the images look like the ones in structured

[jklymak]

Do we particularly want to add ecdf? It's a convenience wrapper of a statistical method more than a plot type and it seems more confusing than helpful to have people look at a step plot and click through to ecdf, which won't do what 99.9% of people who want a step plot will want to do.

[story645]

seems more confusing than helpful to have people look at a step plot and click through to ecdf,

Why would this happen? Wouldn't clicking ecdf lead to ecdf, which is a super popular statistical plot type.

[jklymak]

People get confused by hist, they will definitely get confused by ecdf.

[QuLogic]

It does get an ecdf caption:

[jklymak]

Sure, but you need to understand what an ecdf is to understand what you are looking at, or what the jargon means. Otherwise it looks like stair.

Conversely I would add up structured grids. People ask how to do this all the time, and advertising it would be potentially helpful.