Make no-duplicate-imports consider namespace imports seperate

[GabrielCastro]

Fixes #3418

PR checklist

• Addresses an existing issue: no-duplicate-imports false positive with namespace imports #3418
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Overview of change:

Fix #3418 See that for details

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

[palantirtech]

Thanks for your interest in palantir/tslint, @GabrielCastro! 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.

[adidahiya]

The original issue #3418 looks to be closed by #4524, so I'm going to close this. Let me know if we should reopen.