[PLT-7814] Upgrade to enzyme-adapter-react-16 and enable unit/components tests a…

[saturninoabril]

Summary

This is the final batch for PLT-7814, resolving existing (and additional) component test failures.

This is resubmitted as branch. Original PR from #303.

Included in this PR:

1. Add make test command
2. Enable unit/components tests at Jenkins build.
3. Add make test to PR checklist
4. Add reducers and selectors folders for test coverage computation
5. Add "clearMocks": true to jest config to automatically clear mock calls and instances between every test.

Ticket Link

Jira ticket: PLT-7814

(UPDATE): Jira ticket to revert component tests - PLT-8133

Checklist

• Ran make check-style to check for style errors (required for all pull requests)
• Added or updated unit tests (required for all new features)
• Touches critical sections of the codebase (Jenkins build, make file)

[crspeller]

Perfect. Thanks!