Add page object elements for suggested reviewers tests

What does this MR do and why?

Adds QA selectors and page object elements for a test that will be added soon.

I'm adding the selectors before the test because the test will run in Staging/Production only first, so the selectors need to be deployed before I can verify that the test will pass.

Part of gitlab-org/quality/testcases#3245 (closed)

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