Rename src/test folder to fix #3072

[aleung]

PR checklist

• Addresses an existing issue: tslint npm package missing './test/parse' #3072
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Overview of change:

Rename src/test folder to src/verify and update all places where import it.

Is there anything you'd like reviewers to focus on?

CHANGELOG.md entry:

[palantirtech]

Thanks for your interest in palantir/tslint, @aleung! Before we can accept your pull request, you need to sign our contributor license agreement - just visit https://cla.palantir.com/ and follow the instructions. Once you sign, I'll automatically update this pull request.

[ajafff]

LGTM
Since noone should import these files directly, it's safe to consider this a bugfix.

If it really breaks someone, we could add back the renamed files as a thin wrapper that just exports everything from the new file.

[ajafff]

Thanks @aleung