Some renames

Summary:
Some non-semantic changes. Mostly an earlier rename that was accidentally done only locally rather than across the codebase

Also support `.spec` test extension, which is more idiomatic Jest, since we don't use the `.node` and `.electron` distinction anymore anyway.

Reviewed By: jknoxville

Differential Revision: D22976438

fbshipit-source-id: f3abedb36cbac1e835295177117ccbca492a67a1

desktop/plugins/sections/src/index.tsx

@@ -37,7 +37,7 @@ import {
   Layout,
 } from 'flipper';
 
-import {FlipperClient, createState, usePlugin, useValue} from 'flipper-plugin';
+import {PluginClient, createState, usePlugin, useValue} from 'flipper-plugin';
 
 const Waiting = styled(FlexBox)({
   width: '100%',
@@ -74,7 +74,7 @@ type FocusInfo = {
   treeNodeIndexPath?: number[];
 };
 
-export function plugin(client: FlipperClient<Events, {}>) {
+export function plugin(client: PluginClient<Events, {}>) {
   const generations = createState<{[id: string]: TreeGeneration}>(
     {},
     {persist: 'generations'},