build: speedy tests on circle by splitting the test files into multiple jobs (#21015)

* build: let circleci divide our test suites in two

* well our tests rely on side affects, thats cool I guess

spec-main/api-browser-view-spec.ts

@@ -1,13 +1,9 @@
-import * as chai from 'chai'
+import { expect } from 'chai'
 import * as ChildProcess from 'child_process'
 import * as path from 'path'
 import { emittedOnce } from './events-helpers'
 import { BrowserView, BrowserWindow } from 'electron'
 import { closeWindow } from './window-helpers'
-import dirtyChai = require('dirty-chai')
-
-const { expect } = chai
-chai.use(dirtyChai)
 
 describe('BrowserView module', () => {
   const fixtures = path.resolve(__dirname, '..', 'spec', 'fixtures')