Improve and consolidate config resolution.

[cpojer]

Summary

This allows --projects to take either a js file, a json file, a package.json file or any folder where it will traverse the tree to find a jest.config.js or package.json file. Also enabled me to roll up the function to find configs into a single one.

Test plan

• Tried it at FB.
• Modified yarn test-examples to have a mix of directory names and configs specified in package.json.
• Totally still needs an integration test. #yolo

[codecov-io]

Codecov Report

Merging #3472 into master will decrease coverage by 2.15%.
The diff coverage is 10.52%.

@@            Coverage Diff             @@
##           master    #3472      +/-   ##
==========================================
- Coverage   64.39%   62.23%   -2.16%     
==========================================
  Files         182      181       -1     
  Lines        6695     6692       -3     
  Branches        5        5              
==========================================
- Hits         4311     4165     -146     
- Misses       2382     2525     +143     
  Partials        2        2

Impacted Files	Coverage Δ
packages/jest-config/src/normalize.js	90.8% <ø> (ø)	⬆️
packages/jest-config/src/index.js	36.36% <0%> (-2.77%)	⬇️
packages/jest-config/src/findConfig.js	20% <11.76%> (-8.58%)	⬇️
packages/jest-config/src/vendor/jsonlint.js	5.72% <0%> (-50%)	⬇️

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[github-actions]

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