[GeoMechanicsApplication] Add method to time loop executor to cancel the loop

[carloslubbers]

📝 Description
Implement the unused rShouldCancel delegate, by setting it on the time loop executor we can cancel runs while they are ongoing

[rubenzorrilla]

Just pointing you to Controller class (see here). I think it might be useful for this kind of purpose.

[rfaasse]

Looks clear, thanks for adding this! I just had an idea to make it a little bit cleaner (very minor change) after that, we're good to go!

[rfaasse]

Just pointing you to Controller class (see here). I think it might be useful for this kind of purpose.

Thanks @rubenzorrilla for pointing to this interface, that's a good suggestion! The only issue here is that it is required to be able to define this function outside of the C++ code through a C-interface, so unfortunately we cannot use the Controller here.