Support '.js', '.cjs', '.json' configs

[the-spyke]

Summary

Fixes #9086 and partially #9225. All 3 extensions are looked in order, allowed for manual specification with --config and supported for initialization in jest-cli.

Test plan

Try configuring Jest with all 3 supported config types: .js, .cjs, .json. Testing .cjs requires running Node >= 13.3.

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[codecov-io]

Codecov Report

Merging #9291 into master will increase coverage by <.01%.
The diff coverage is 90.9%.

@@            Coverage Diff             @@
##           master    #9291      +/-   ##
==========================================
+ Coverage   64.98%   64.99%   +<.01%     
==========================================
  Files         278      278              
  Lines       11899    11912      +13     
  Branches     2934     2935       +1     
==========================================
+ Hits         7733     7742       +9     
- Misses       3537     3539       +2     
- Partials      629      631       +2

Impacted Files	Coverage Δ
packages/jest-config/src/index.ts	11.76% <0%> (-0.18%)	⬇️
packages/jest-config/src/constants.ts	100% <100%> (ø)	⬆️
packages/jest-config/src/resolveConfigPath.ts	92% <100%> (+1.09%)	⬆️
packages/jest-cli/src/init/constants.ts	100% <100%> (ø)	⬆️
packages/jest-cli/src/init/index.ts	81.81% <83.33%> (-1.91%)	⬇️
packages/expect/src/utils.ts	94.93% <0%> (-1.27%)	⬇️

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[SimenB]

This is wonderful, thank you! Could you add an e2e test using a cjs file? It can be skipped on nodes older than 13.2

[SimenB]

I just made the changes myself as they're minor. Thanks again for the PR! (will merge when/if green)

[the-spyke]

@SimenB I was too late :-)

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