Reformat contour state

[johallar]

⚠️ This is built on top of the polygons stuff, so I set the target branch to that for diff's sake. Will merge this after that one and rebase on master

This also includes popups in the contour demo and some small changes around that

Merge Checklist

:wrench: Issue(s) fixed:

• [ ] Author referenced issue(s) fixed by this PR:
• [ ] Fixes #0

:smoking: Smoke Test

• [ ] Works in chrome
• [ ] Works in firefox
• [ ] Works in safari
• [ ] Works in ie edge
• [ ] Works in ie 11

:ship: Merge

• [ ] author crafted PR's title into release-worthy commit message.

[johallar]

Thanks for the thorough review, I think we could go pretty deep on validation, but for now if you pass an invalid spec its gonna break, and the structure of the spec passed from immerse is quite static so should minimize the risk here.

I made https://heavyai.atlassian.net/browse/FE-16036 so I won't forgot to follow up once we have some breathing room