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/api-shell-spec.js

@@ -1,5 +1,4 @@
-const chai = require('chai')
-const dirtyChai = require('dirty-chai')
+const { expect } = require('chai')
 
 const fs = require('fs')
 const path = require('path')
@@ -7,9 +6,6 @@ const os = require('os')
 const http = require('http')
 const { shell } = require('electron')
 
-const { expect } = chai
-chai.use(dirtyChai)
-
 describe('shell module', () => {
   const fixtures = path.resolve(__dirname, 'fixtures')
   const shortcutOptions = {