Fix annotation autorange on category axes

[etpinard]

fixes #1768 by making the category axes setConvert methods a bit more of a mess. Note that annotation autorange uses ax.r2c.

Oh well, with this patch here, it seems like all the cases are covered.

Together with #1748, we now have working category annotations on first draw and on pan/zoom 🎉 :

By the way @alexcjohnson I chose to add a new mock in f5c0382 instead of appending annotation-autorange.json to test shapes on category axes as well. I hope you don't mind.

[alexcjohnson]

Nice and simple, and this actually seems like it's the logical way for ax.r2c to work. No problem about splitting off the mock - you're right to include both x and y, shapes and annotations (what about images?) - though at some point I feel like a bit of consolidation may be in order.

But did that mock fail before the patch? The coordinates that lead to the shape and annotations bumping out the autorange didn't come from category names. For annotations we can use a category that's already in the data and let the text box or arrow add extra pixel padding, for shapes it seems like we may need to use a category that's not in the data, so ax.categoryarray?

[etpinard]

@alexcjohnson

Nice and simple, and this actually seems like it's the logical way for ax.r2c to work.

Great.

(what about images?)

Layout-image-induced autorange bumps aren't a thing ye (seet #1111) and the layout_image mock already has a category axis. But yeah, when #1111 will be completed, we should add an image or two to category-autorange.json.

But did that mock fail before the patch?

Oops, I messed that up when I added arrows to the mock. Fixed in -> e4aa7a3

for shapes it seems like we may need to use a category that's not in the data, so ax.categoryarray?

Good call here. That actually uncovered another bug. Done in -> aaf12ba

Bonus: annotations and shapes with invalid category coordinates were broken too. Fixed in -> 0758b3b

[alexcjohnson]

Beautiful. Gotta love it when all these extra edge cases pop out on fixing related issues.
💃