renamed tr-tests GHA to tr-unit-tests

[bueale]

What does this PR (Pull Request) do?

• This PR fixes Rename tr-tests github action to tr-unit-tests for clarity of scope #5436

Which Traffic Control components are affected by this PR?

• Traffic Router
• .github/actions/tr-unit-tests/action.yml
• .github/actions/tr-unit-tests/README.md
• .github/workflows/tr.unit.tests.yaml

What is the best way to verify this PR?

On the GitHub Actions run page: Run unit tests

If this is a bug fix, what versions of Traffic Control are affected?

The following criteria are ALL met by this PR

• This PR includes tests
• This PR does not require necessary documentation updates.
• This PR includes NO necessary changes to CHANGELOG.md
• This PR includes any and all required license headers
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

Additional Information

[mitchell852]

@alebricio - make sure you complete the PR template

[zrhoffman]

Everything changed so far looks fine. On the GitHub Actions run page:

1.Can tests be reworded?
2. Can Run unit tests be reworded to specify which unit tests are being run?

[alebricio]

@alebricio - make sure you complete the PR template

@mitchell852 I believe this was intended for @bueale

[mitchell852]

@alebricio - make sure you complete the PR template

@mitchell852 I believe this was intended for @bueale

haha. sorry. @bueale ^^ also, no need to put the issue in the title. that's what the PR template is for. :)

[zrhoffman]

Looks good! On second thought, no need to rename the test job, because there is only 1 job, and all places where it is mentioned, you can see the name of the workflow anyway.