fix(cleanup): microtask flushing now supports fake timers

[kentcdodds]

What: microtask flushing now supports fake timers

Why: So people can use fake timers in their react tests without it causing issues with React's scheduler

How:

• Three days of total pain and anguish...
• Detect whether we're using fake timers and if we are, advance them forward.

Checklist:

- [ ] Documentation added to the docs site N/A
- [ ] Tests N/A (really really hard to reproduce)
- [ ] Typescript definitions updated N/A

• Ready to be merged
  

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[codecov]

Codecov Report

Merging #720 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #720   +/-   ##
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  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          100       100           
  Branches        16        16           
=========================================
  Hits           100       100           

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[kentcdodds]

🎉 This PR is included in version 10.4.2 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[9still]

@kentcdodds Just stumbled on this - Thanks for fixing this! FYI: I just filed jestjs/jest#10555 to hopefully get jest to provide an official way to find out if fake timers are being used. Just referencing this here so if the API is added there, appropriate changes can be made.