fix(react): remove generated styles.[ext] file for CSS-in-JS solutions like styled-compoentns/emotion (#4347)

packages/react/src/schematics/application/application.spec.ts

@@ -482,6 +482,9 @@ describe('app', () => {
         tree.exists('apps/my-app/src/app/app.styled-components')
       ).toBeFalsy();
       expect(tree.exists('apps/my-app/src/app/app.tsx')).toBeTruthy();
+      expect(
+        tree.exists('apps/my-app/src/styles.styled-components')
+      ).toBeFalsy();
 
       const content = tree.read('apps/my-app/src/app/app.tsx').toString();
       expect(content).toContain('styled-component');

packages/react/src/schematics/application/files/global-css/src/styles.__style__

@@ -0,0 +1 @@
+/* You can add global styles to this file, and also import other style files */