Removing select and scatter kernel unit test

[aws-shchung]

Issue #, if available:

<Fill ME>

Description of changes:

Remove select and scatter kernel unit test, dropping support for this

Testing:

Please see detailed unit test requirements in the CONTRIBUTING.md

• The change is covered by numeric check using nki.baremetal
• The change is covered by performance benchmark test using nki.benchmark
• The change is covered by end-to-end integration test

Pull Request Checklist

• I have filled in all the required field in the template
• I have tested locally that all the tests pass
• By submitting this pull request, I confirm that my contribution is made under the terms of the MIT-0 license.

[tonyz0x0]

LGTM