Optimize CommentContainer.spec.tsx test initialization

[nick-funk]

What does this PR do?

Use waitFor and getByTestId for the initialization of the CommentContainer.spec.tsx tests.

This cuts a problematic test render username and body's render time down from roughly 1320ms to 795ms. Since we're seeing this test take minutes to run on GitHub Actions CI, this should help it finish without timing out.

I realize replacing a findBy with a waitFor + get is considered less optimal for most occasions, I have documented why this is more optimal in the code. Several folks have found this to be the case for finding objects in particularly large test DOM's on StackOverflow and GitHub issues. For now, this is a nice quick fix to get some speed during a particularly slow test.

These changes will impact:

• commenters
• moderators
• admins
• developers

What changes to the GraphQL/Database Schema does this PR introduce?

None

Does this PR introduce any new environment variables or feature flags?

No

If any indexes were added, were they added to INDEXES.md?

No new indices.

How do I test this PR?

• run the tests
• see that they pass
• watch that it passes more reliably in CI

Where any tests migrated to React Testing Library?

No

How do we deploy this PR?

No special considerations.

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[kabeaty]

very nice!