Resolve "Add tests for "Redesign projects lists UI""

What does this MR do?

Adds missing tests for project list UI redesign:

In particular, it adds tests for the following methods:

• explore_projects_tab? in projects_helper.rb
• show_merge_request_count? inprojects_helper.rb`
• show_issue_count? in projects_helper.rb

In addition, it adds a test to overview_spec.rb to test if the compact class is set correctly.

Moreover, it changes the interface of the helper methods show_merge_request_count? and show_issue_count?.

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/55359

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer

Closes #55359 (closed)