Remove expectations from tests

[NeedleInAJayStack]

We were getting a few of the following warning in the test code:

warning: 'expectation' mutated after capture by sendable closure

This resolves the warnings by removing unnecessary use of expectation in the unit tests, replacing them with try Future.wait(). I took this opportunity to refactor these tests to simplify them to atomic XCTAssertEquals calls. I also removed the unused allTests extensions.

There were no functional changes to the tests themselves.