Ant tree -> React complex tree

Summary:
Upgraded from ant tree library to the much more capable React complex tree. Added the following:
1. Ability to expand / collapse nodes while automatically expanding / collapsing active/inactive children when they change
2. Keyboard controls of tree all the time
3. Basic search functionality
4. Selecting node in tree focuses and scrolls in the tree
5. Hover state for tree

Reviewed By: lblasa

Differential Revision: D40633876

fbshipit-source-id: 8dcef5ec2c277e476a3eb3cdaef62b15c25323c0

desktop/themes/base.less

@@ -7,6 +7,7 @@
  */
 @import '../node_modules/antd/dist/antd.less';
 @import './typography.less';
+@import (inline) './plugins/public/node_modules/react-complex-tree/lib/style.css';
 /* Based on: https://www.figma.com/file/4e6BMdm2SuZ1L7FSuOPQVC/Flipper?node-id=620%3A84636 */
 @background-transparent-hover: rgba(0, 0, 0, 0.1);