This PR has a large blast radius because it takes the final step and bumps up the Controller to be fully async.
We have historically done a piece-by-piece update, so all operations were already async but the controller interface was kept synchronous.
With this update, the controller is now fully async and all tests are updated.
Most places where the new C# compiler warns about function names not ending in `Async` were also adressed, giving a massive refactor change.
Functionally, no changes are done.
According to the current implementation, the progress bar does not advance
when files are skipped by FilePreFilterProcess. This causes users'
confusion since the web frontend will get stuck at a certain stage for a
long time. This commit addresses this issue.
Kenneth Skovhede