Make Rails/HttpStatus aware of Rails specific response assertions

[tldn0718]

This PR makes the HttpStatus Cop aware of the Rails-specific assertions that test responses from Rails applications, such as assert_response and assert_redirect_to.

This Cop enforces a consistent method of specifying HTTP status in render, redirect_to, and head, either symbolic or numeric. However, it did not account for assert_response and assert_redirect_to used in testing, which also accepts HTTP status as a parameter in a manner consistent with those methods.

This PR ensures that the HttpStatus Cop can enforce a uniform way of specifying HTTP status in both application and testing code. Specifically, it addresses the previously possible inconsistency in specifying HTTP Status when using assert_response and assert_redirect_to.

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Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.
• If this is a new cop, consider making a corresponding update to the Rails Style Guide.

[koic]

Let's proceed with this. Thanks!