Allow custom resolver to be used with[out] moduleNameMapper

[midzelis]

Also, improve error message when moduleNameMapper doesn't resolve to a module.

Summary

1. The existing moduleNameMapper implementation doesn't invoke the customer resolver with the custom resolver option. This makes it impossible to write custom resolvers that work in all cases.
2. If a moduleNameMapper was not specified, then the custom resolver would not be run at all.

This PR solves the two problems above.

1. It passes through the resolver configuration option so that the custom resolver could be used after the moduleMapMapper mapped the module. Additionally, the error message was improved with exactly which moduleName (including the mapped version) was causing the problem.
2. If the moduleNameMapper isn't specified, it sends everything through to the resolver, unmapped. Additionally, the rootDir is passed to the resolver, to help it aid resolution, in case it may be dependent on the rootDir config option.

Test plan
Added 2 tests. Configuration documentation were updated with new argument passed to custom resolver.

[codecov-io]

Codecov Report

Merging #4174 into master will increase coverage by 0.37%.
The diff coverage is 90.9%.

@@            Coverage Diff             @@
##           master    #4174      +/-   ##
==========================================
+ Coverage   56.17%   56.55%   +0.37%     
==========================================
  Files         191      191              
  Lines        6424     6426       +2     
  Branches        6        6              
==========================================
+ Hits         3609     3634      +25     
+ Misses       2812     2789      -23     
  Partials        3        3

Impacted Files	Coverage Δ
...ackages/jest-cli/src/reporters/default_reporter.js	91.42% <ø> (ø)	⬆️
packages/jest-config/src/index.js	0% <ø> (ø)	⬆️
packages/jest-runtime/src/index.js	85.71% <ø> (ø)	⬆️
packages/jest-resolve/src/default_resolver.js	3.33% <ø> (ø)	⬆️
packages/jest-runner/src/run_test.js	4.44% <ø> (ø)	⬆️
packages/jest-cli/src/run_jest.js	0% <0%> (ø)	⬆️
packages/jest-resolve/src/index.js	36.69% <100%> (+22.67%)	⬆️
packages/jest-cli/src/reporters/utils.js	61.38% <100%> (ø)	⬆️

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[midzelis]

@cpojer whats the status of this PR? Am I missing anything before it can committed?

[midzelis]

@cpojer whats the status of this PR? Am I missing anything before it can committed?

[cpojer]

You'll need to rebase this diff, otherwise we'll be unable to merge it. I'm fine with these changes, and the cwd changes should fix a few other issues also. Thanks for contributing.

[cpojer]

Could you try pushing to this branch again? Seems like all builds failed for some reason.

[midzelis]

Closing/reopening to trigger integration tests: circleci/appveyor/travis-ci

[cpojer]

Thanks for your contribution. This was definitely a rough edge in Jest and a missing feature for as long as moduleNameMapper has existed, so I'm glad you contributed a fix for it. In the next few days (possibly tomorrow) I'll release a test release with this code under jest@test. Watch our for that!

[midzelis]

Thanks for merging!

[github-actions]

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