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

app/components/EventBoundary.js

@@ -4,13 +4,18 @@ import * as React from "react";
 
 type Props = {
   children: React.Node,
+  className?: string,
 };
 
-export default function EventBoundary({ children }: Props) {
+export default function EventBoundary({ children, className }: Props) {
   const handleClick = React.useCallback((event: SyntheticEvent<>) => {
     event.preventDefault();
     event.stopPropagation();
   }, []);
 
-  return <span onClick={handleClick}>{children}</span>;
+  return (
+    <span onClick={handleClick} className={className}>
+      {children}
+    </span>
+  );
 }