[Bug] Faster Log Devices don't Release Lock on File After Dispose.

### Running
```csharp
_store.Log.FlushAndEvict(true);
_store.Dispose();
```

FasterDb still has a lock on the device files. Files are only freed when you exit process.

### Exception
```
System.IO.IOException: The process cannot access the file 'DATA.0' because it is being used by another process.
```