SG-41170: Restore QMessageBox as the alertPanel() cmd implementation

[bernie-laberge]

SG-41170: Restore QMessageBox as the alertPanel() cmd implementation

Linked issues

NA

Describe the reason for the change.

With the aim of fixing a Tahoe Qt specific issue, the alertPanel()'s implementation was recently changed to use a custom QAlertPanel instead of a QMessageBox.
This solved the Tahoe issue but some other issues were found with the new QAlertPanel based implementation: alertPanel() could be resized and it would truncate text when increasing RV font size.

Now instead of fixing all these new issues in the new QAlertPanel, and for the sake of uniformization since that the RV C++ code is using QMessageBox, NOT QAlertPanel (only the alertPanel() command used by mu and python plugin are making use of the new custom QAlertPanel), we decided to take another look at how we could solve the original Tahoe specific issue with the unclickable button.

After some investigation, we realized that the original Tahoe specific issue could be solved by ensuring that the widget-based implementation is used instead of the native dialog:
QApplication::setAttribute(Qt::AA_DontUseNativeDialogs);

This way, both the mu+python alertPanel command and the RV C++ code can use the original QMessageBox as it has been doing in the last 15 years.

Summarize your change.

On macOS, now ensuring that the widget-based implementation is used instead of the native dialog:
QApplication::setAttribute(Qt::AA_DontUseNativeDialogs);

Restore the QMessageBox original used in the alertPanel() command implementation

Describe what you have tested and on which operating system.

Successfully tested on macOS Sequoia 15.7.2 andd macOS Tahoe 26.1

Add a list of changes, and note any that might need special attention during the review.

If possible, provide screenshots.

Before - alertPanel shows truncated text:

Before - alertPanel can be resized (it should not):

After - On macOS Tahoe: (and the buttons are working)