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.
This PR handles a case where the `dindex` files may reference non-existing `dblock` files. In this case the recreate may register missing (and unused) blocks in the `DeletedBlock` table, which will later cause issues if the blocks are attempted used.
The fix is to remove missing blocks before the cleanup so there is no entry that references the missing volumes.
This fixes issue #6552
Kenneth Skovhede