Checkbox tree fixes

[allisonking]

Closes #743

Code Changes

• Icon fixes for arrow up and arrow down icons
• Expanded state which is separate from selected state
• Indeterminate state when not all children of a parent are selected
• Checking a child makes parent "checked" (or indeterminate) but not "selected"
• When a parent is checked, all of its children are also checked, but disabled

Steps to Confirm

• Play around at http://localhost:3000/taxonomy

Pre-Merge Checklist

• All CI Pipelines Succeeded
• Documentation Updated:
  • documentation complete, or draft/outline provided (tag docs-team to complete/review on this branch)
  • documentation issue created (tag docs-team to complete issue separately)
• Issue Requirements are Met
• Relevant Follow-Up Issues Created
• Update CHANGELOG.md

Description Of Changes

There are a lot of UX things baked into this checkbox for our use case, so the easiest way to see if it is working as expected is probably just to play with it yourself. Hopefully the tests cover all of the cases too.

Screen.Recording.2022-06-14.at.1.46.52.PM.mov

[ThomasLaPiana]

LGTM! One small UX nit

[ThomasLaPiana]

@allisonking This is potentially for another issue but something I'd suggest from a UX perspective is that when I click "between" the arrow and the category itself (the dead space) it doesn't do anything. This felt unintuitive, as I'd expect it to either trigger the drop down (first choice) or select the category (second choice). Clicking on it and having nothing happened felt a bit off because the row was still highlighted