TotalSegmentor is launched as a blocking process

[BishopWolf]

TotalSegmentor is launched as a blocking process that hangs Slicer for several minutes. It shall be remade as a process with progress bars. I think this is self explanatory.

[lassoan]

I don't plan to work on this but it would be nice if you could make this change.

The segmentation already runs in a separate process, so probably all the logic change you is to replace the while loop in logProcessOutput by a timer callback. Make the blocking/non-blocking behavior selectable by adding a waitForCompletion argument (=True by default) to the in process method. Blocking mode is required for batch processing and makes things simpler when the logic is used from other modules.

The GUI need to be tuned a bit, too: remove the override cursor, add some kind of a progress bar (it is not trivial to determine an accurate progress from the process output), and turn the Apply button to Cancel button while the segmentation is running (clicking it will terminate the process).