Transition to PySide6

[qku]

Description

I played around with qudi-core and the dummies in qudi-iqo-modules trying to make them compatible with PySide6/Qt6.

Most changes are either

• replacements of from PySide2 import ... with from PySide6 import ...
• replacements of QtWidgets.QAction with QtGui.QAction
• changes to constants: something like self.DockWidgetFloatable had to be changed to QtWidgets.QDockWidget.DockWidgetFloatable to get it working

The more complicated changes are in 63a0a4f affecting the POI manager and the pulsed toolchain. Some signals seem to have changed in Qt6. Since I don't know the modules very well, I am not sure if the changes I made don't break anything. As an example, I found that I cannot delete POIs in the dummy anymore.

Motivation and Context

I am sure that there are many good reasons to eventually transition to PySide6. Personally, I was motivated to play around with this since I am mostly developing on a laptop with Apple Silicon processor which does not support PySide2.

How Has This Been Tested?

Not very thoroughly: I loaded all dummy modules in the default config and pressed a few buttons at random.

Types of changes

• Bug fix
• New feature
• Breaking change (Causes existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• I have documented my changes in /docs/changelog.md.
• My change requires additional/updated documentation.
• I have updated the documentation accordingly.
• I have added/updated the config example for any module docstrings as necessary.
• I have checked that the change does not contain obvious errors
  (syntax, indentation, mutable default values, etc.).
• I have tested my changes using 'Load all modules' on the default dummy configuration.
• All changed Jupyter notebooks have been stripped of their output cells.

[qku]

See also the corresponding PR to qudi-core: Ulm-IQO/qudi-core#45