feat(jest-core): allow using Summary Reporter as stand-alone reporter

[mrazauskas]

Inspired by rickhanlonii/jest-silent-reporter#29

Summary

Currently there is no way to use only Summary Reporter. For instance, it might be useful together with Silent Reporter or simply as stand-alone reporter (that’s even more silent, why not?).

This idea came to my mind, while refactoring setupReporters() logic. Hence, this PR simplifies logic, adds more tests and one nice feature.

Test plan

More tests added. All should pass.

[SimenB]

I like it!

[Hypnosphi]

Before this change, all the custom reporters were being added after the built-in ones like CoverageReporter: https://github.com/facebook/jest/pull/12687/files#diff-18559c2ed95cf75fe249b47a0c70cf994dc0fa2a2f34727df4e6eb2f0e683cc5L370
This way it was possible to use coverageMap in a custom reporter. Now they are added before. I think this should be marked as a breaking change in the changelog

[mrazauskas]

Ah.. Right, did not realise there could be such use case. Easy to move coverage reporter before custom. It felt like it makes sense to keep summary as the last one. Or?

[github-actions]

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