26834 merge crash

#26834: [tk-3dsmaxplus] 3ds Max is crashing if we merge 2 objects with the same name
this seems to be a hotspot - we call out to `MaxPlus.Core.EvalMAXScript` which may pop up a UI of a different flavour which confuses things and means you have to special window focusing code. How about adding an `engine.safe_eval_maxscript()` method (or similar) which wraps around this command and ensures UI consistency for the QT side of things? Then the hook (and other code) can just call that. And we document that command and make it part of the official 3dsmax engine and recommended behaviour.