Add new asset menu system

[paulkaplan]

This is a WIP, I'm working on getting the tests back

Resolves

What Github issue does this resolve (please include link)?

Resolves #1166

Proposed Changes

Describe what this Pull Request does

There are a fair number of changes here.

• Update the asset button class to take in more options, totally redesigning the menu system.
• Add new methods for adding surprise sprite/costume/backdrop/sounds.
• Add new methods for adding empty sprites / backdrops, which also switch the tab focus to the paint editor.

There are things that will need refactoring, but we are going to wait until we can actually test this with people to learn more about the usability of these menus.

A refactor of the way tooltips are styled should also be considered with the next time we use tooltips, like the import modal work. For now, there is a fair bit of duplicated-ish CSS for controlling the tooltips.

Testing

I'm in the process of updating the tests.

[rschamp]

Try it out: asset-menus

I'm a bot, not actually @rschamp!

[mrjacobbloom]

The wait time before closing solves all the problems I was worried about in terms of missing the buttons with the mouse, this feels really natural! Great job you guys!

The closing animation feels a little linear to me but that's no big