Description

• Migrate most Mocha-based unit tests to Jest
• Move non-migrated Mocha tests from /test/unit to test/mocha. It's really just 1 test file, plus a helper mock file.
• Add eslint-plugin-jest, specifically for jest/globals lint rule
• Add test/unit/.eslintrc that includes updated semi and quotes` lint rules
• Update package test script names for clarity, and update documentation accordingly

Note: The WIP non-migrated Mocha test remains, but is skipped for Jest.

Motivation and Context

Recent feature: es2105 artifacts introduced Jest test environment. This PR continues the migration from Mocha to Jest.

How Has This Been Tested?

These tests pass. :)

Test Suites: 1 skipped, 30 passed, 30 of 31 total
Tests:       23 skipped, 434 passed, 457 total
Snapshots:   0 total
Time:        16.554 s

Screenshots (if appropriate):

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.