Remove unused stuff

[RafaelJCamara]

Description

Removed unused references, and variables. Simplified namespaces. Adjusts in tests, because their build was failing because of not awaiting async method calls.

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• [X] Code compiles correctly
• [X] Created/updated tests
• [ ] Extended the documentation

[RafaelJCamara]

While I appreciate the effort to cleanup the codebase--and there's plenty to do there--this is a hefty PR. While the changes all appear individually trivial, it would be easy to miss a change that might have unintended consequences. I would prefer to split this up into several PRs that each address a particular thing (e.g. removal of unused using statements, another that cleaned up unused fields/values, etc.) which will make the changes easier to review.

I'll split that in multiple PRs! Thank you so much for the feedback!