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/asar-spec.js

@@ -1,5 +1,4 @@
-const chai = require('chai')
-const dirtyChai = require('dirty-chai')
+const { expect } = require('chai')
 const ChildProcess = require('child_process')
 const fs = require('fs')
 const path = require('path')
@@ -9,9 +8,6 @@ const nativeImage = require('electron').nativeImage
 
 const features = process.electronBinding('features')
 
-const { expect } = chai
-chai.use(dirtyChai)
-
 async function expectToThrowErrorWithCode (func, code) {
   let error
   try {