Very poor performance on basic tests

## 🐛 Bug Report

I've created a simple test with no configuration. You can find it [here](https://github.com/cozmy/jest-performance). It takes 7.6 seconds just to start jest, and then, on file change, it takes 5 seconds to re-run.
There's clearly something wrong here.

Mocha and Chai, for example, start in around 4 seconds, but afterward, the re-run is almost instant.

It's weird that Jest reports that the test takes 14ms but shows me the result in 5 seconds.


On top of this, if you add more basic tests, the time just seems to go up.


## To Reproduce

Clone [my minimal repository](https://github.com/cozmy/jest-performance), `yarn install` and `yarn test`.

## Expected behavior

It should be faster than this.

## Link to repl or repo (highly encouraged)

https://github.com/cozmy/jest-performance

## Run `npx envinfo --preset jest`

Paste the results here:

```
System:
OS: Windows 10
CPU: (8) x64 Intel(R) Core(TM) i7-4700MQ CPU @ 2.40GHz
Binaries:
Node: 8.12.0 - C:\Program Files\nodejs\node.EXE
Yarn: 1.13.0 - C:\Users\CosminCristian\AppData\Roaming\npm\yarn.CMD
npm: 6.8.0 - C:\Program Files\nodejs\npm.CMD
```

Clone the linked minimal repository, run yarn install and yarn test, and compare the reported startup and file-change rerun times on the supplied Windows environment. Read the issue comments for any narrowed scope or proposed direction; done means reproducing the delay and identifying a concrete performance regression or actionable cause in Jest.

Written by the indexing model from the issue text.