fix: Keyboard accessible context menus (#1768)

- Makes menus fully accessible and keyboard driven
- Currently adds 2.8% to initial bundle size due to the inclusion of Reakit and its dependency, popperjs.
- Converts all menus to functional components
- Remove old custom menu system
- Various layout and flow improvements around the menus

closes #1766

package.json

@@ -152,6 +152,7 @@
     "react-virtualized-auto-sizer": "^1.0.2",
     "react-waypoint": "^9.0.2",
     "react-window": "^1.8.6",
+    "reakit": "^1.3.4",
     "rich-markdown-editor": "^11.0.11",
     "semver": "^7.3.2",
     "sequelize": "^6.3.4",