Use string representation for QKeySequence construction

[mborgerson]

This fixes an issue in PySide6 v6.6.2 where key sequence construction with the | operator is broken, and improves readability.
Ideally this would be fixed in PySide6 or qtpy to retain original behavior, but since it also improves readability I think it makes sense to fix it here too.

Broken with PySide6 v6.6.2:

from qtpy import QtCore
QtCore.Qt.AltModifier | QtCore.Qt.Key.Key_C
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[2], line 1
----> 1 QtCore.Qt.AltModifier | QtCore.Qt.Key.Key_C

TypeError: unsupported operand type(s) for |: 'KeyboardModifier' and 'Key'

[mborgerson]

Hi @ccordoba12, would you mind taking a look at this patch? The failing CI appears to be unrelated to the patch.

[ccordoba12]

Looks good to me, thanks @mborgerson!

(Sorry for the delay in reviewing your work. This one just missed my radar).