Use Test<Object>s naming convention for WebAuthn test object factories

[vasanth-79]

Issue Number: 16604

Renamed the WebAuthn Test Object class names.

Refactored class names to follow pluralized naming pattern.
Updated all instances in the codebase where these class names were used to ensure consistency.
Updated related references in the code to match the new class names.

[jzheaux]

Thank you, @vasanth-79! This is now merged into main. I hope to see more contributions from you in the future! Please look for the status: ideal-for-contribution label on tickets.

Also, and this is just a minor thing, you might notice that this PR says "closed" instead of "merged". It was indeed merged in 04d7130 and 4cdc6da; however, I couldn't push these polishes to the PR since it was from your main branch. For future PRs, you can cut a branch, like gh-16604 and that makes it possible for me to push the polishes to that branch and we merge the PR from here.