RN: Flowify `packages/react-native/jest`

[yungsters]

Summary:

Adds @flow (or @noflow) to all files in this directory and ensures that Flow succeeds (by adding type annotations, using minor refactors, or suppressing errors due to intentionally dynamic logic).

This will help improve type safety when making changes both in these files as well as files that these depend on.

Changelog:

[Internal]

Test Plan:

Ran Flow and Jest tests successfully:

$ yarn flow
$ yarn test

[facebook-github-bot]

@yungsters has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D75488160

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D75488160

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D75488160

[react-native-bot]

This pull request was successfully merged by @yungsters in a4c20070689ee137891a9f6f8ecc92d0f56b13ef

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[facebook-github-bot]

@yungsters merged this pull request in facebook/react-native@a4c20070689ee137891a9f6f8ecc92d0f56b13ef.