[webpack 4] third time's the charm ;) (#5370)

* [perf] add webpack 4 + SplitChunks + lazy load visualizations (#5240)

* [webpack] setup lazy loading for all visualizations

* [lazy-load] push renderVis function to <Chart /> state

* no mapbox token

* [lazy loading] use native webpack import func to fix chunk names, add babel-plugin-syntax-dynamic-import, fix rebase bug.

* fix geojson import, undefined t, and fix async css bug

* [lazy load] actually add babel-plugin-syntax-dynamic-import

* [webpack] working dev version of webpack v4

* [webpack 4] fix url issues, use mini-css-extract-plugin and webpack-assets-manifest plugins

* [webpack 4] use splitchunks for all files, update templates to multi-file entrypoints

* [webpack 4] multiple theme entry files for markup vis css, don't uglify mapbox

* [webpack 4] lint python manifest changes, update yarn lock.

* [webpack 4] fix tests with babel-plugin-dynamic-import-node

* [webpack 4] only use 'dynamic-import-node' plugin in tests, update <Chart /> vis promise when vis type changes

* [webpack 4] clean up package.json and yarn.lock after rebase

* [webpack 4] lint?

* [webpack 4] lint for real

* [webpack 4][istanbul] ignore visualizations/index.js

* [webpack 4] fix rebase bug, update dashboard/deprecated/chart/Chart.jsx to use vis promises.

* [webpack 4] lint and test

* [webpack 4] yarn.lock

superset/assets/spec/javascripts/chart/Chart_spec.jsx

@@ -38,10 +38,10 @@ describe('Chart', () => {
       <Chart {...mockedProps} />,
     );
   });
-  describe('renderViz', () => {
+  describe('renderVis', () => {
     let stub;
     beforeEach(() => {
-      stub = sinon.stub(wrapper.instance(), 'renderViz');
+      stub = sinon.stub(wrapper.instance(), 'renderVis');
     });
     afterEach(() => {
       stub.restore();