This makes it possible to have the right laser code set for hot start
aircraft that (typically) do not allow changing laser codes when the
engine is on.
It sounds like PySide2 will not be moving to Python 3.11, so we're stuck
on 3.10 without this. Upgrading to a newer Qt also fixes some high DPI
bugs (the file browser dialog for save/load is no longer tiny on 4k).
https://github.com/pyinstaller/pyinstaller/issues/5414 previously
blocked this, but the bug appears to be fixed now.
This appears to be incompatible with pyinstaller. I get the following
when trying to run the executable generated with pyside6:
```
Traceback (most recent call last):
File "qt_ui\main.py", line 29, in <module>
File "PyInstaller\loader\pyimod03_importers.py", line 476, in exec_module
File "qt_ui\windows\QLiberationWindow.py", line 28, in <module>
File "PyInstaller\loader\pyimod03_importers.py", line 476, in exec_module
File "qt_ui\widgets\map\QLiberationMap.py", line 11, in <module>
ImportError: could not import module 'PySide6.QtPrintSupport'
```
Aircraft that have no loadouts at all (such as the IL-78M) will have no
loadouts and thus no values in the dropdown menu. If the player toggles
the custom layout box we reset the flight's loadout to the selected
loadout, and with no loadouts in the combo box that is None, and
`Flight.loadout` isn't supposed to be optional.
Check for that case in the loadout selector and replace with an empty
loadout if that happens.
Fixes https://github.com/dcs-liberation/dcs_liberation/issues/1402
Loadout selection no longer has two (disagreeing) implementations. What
the UI shows is now what the miz will have.
We now store the chosen layout in the Flight *always*, not just for
custom loadouts. This means that we do loadout lookups at the start of
each turn, but the data is cached in pydcs.
Era-specific loadout degradation is still done at generation (and
presentation) time. This is so that players can toggle that option and
have it affect the *current* turn, rather than the next one.
