Tuner usability enchancements

[jcolafrancesco]

This pull request introduces several improvements to the Tuner dialog and simulation abort handling, with a focus on enhancing the user experience during parameter tuning and simulation reruns. The main changes include persistent storage and restoration of tuner parameters and ranges, improved simulation progress feedback, and robust logic to abort and restart simulations when tuning parameters are changed rapidly.

Tuner dialog enhancements:

• Persistent storage of tuner parameter ranges and active elements, allowing the Tuner dialog to remember user selections and value ranges across open/close cycles. (tuner.cpp, tuner.h) [1] [2] [3] [4] [5] [6]
• Automatic restoration of previously selected tuner parameters and their value ranges when reopening the Tuner dialog. (tuner.cpp)
• Persistent saving of min/max/step values when the user changes them, ensuring their values are not lost. (tuner.cpp) [1] [2] [3] [4]

Simulation progress and abort logic:

• Improved progress bar handling: switches to an indeterminate "busy" state during simulation, resets after completion, and disables/enables UI appropriately. (tuner.cpp) [1] [2] [3]
• Introduced a timer to abort and restart simulations if a new parameter change arrives while a simulation is running, preventing lag and ensuring the latest parameter is always simulated. (tuner.cpp, tuner.h) [1] [2] [3]
• Added logic to explicitly abort running simulations via a new slotAbortTuningSimulation method in QucsApp, supporting both internal and external simulators. (qucs.cpp, qucs.h, simmessage.h, externsimdialog.h) [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Other improvements:

• The Tuner dialog now opens at the top-left of the main window for better visibility. (qucs.cpp)

These changes collectively make the Tuner dialog more robust and user-friendly, especially during rapid parameter adjustments and simulation reruns.