feat: use qtpy and add support for pyside6

[justinsaws]

What was the problem/requirement? (What/Why)

We currently use Pyside2 for our GUI requirements (brought in by external applications) but want to be able to use pyside2, pyside6, or other qt-based runtimes (ie. whatever other applications may provide).

What was the solution? (How)

Switching to use QtPy allows us to abstract away the choice of which specific Qt bindings to use and makes switching a fairly seamless process.

The main changes here are:

• add qtpy to pyproject
• swap all pyside2 references to qtpy
• add optional GUI deps. Invoked by pip install deadline[gui]
• add the ability for the deadline cli to install gui deps at runtime by asking the user, regardless of the standard python or deadline executable
• fix how we were creating signals to be pyside2/6 compatible
• swap QRegExpValidator to QRegularExpressionValidator, since qtpy is missing that compatibility and the former is no longer available in pyside6, but the latter is available in both.
• fix maximum recursion depth issue by removing deprecated exec_ references

There's still some clean-up that can be done, as evidenced by needing some mypy overrides.

What is the impact of this change?

• user experience is greatly improved by having easy access to the GUI, even if they started with CLI
• default gui experience with deadline cloud is now PySide6
• Future Qt development should be simplified
• we can support GUIs on python 3.11 or later
• we can support GUIs on macOS arm

How was this change tested?

Standard tests

hatch run fmt
hatch build
hatch run lint
hatch run test

Ran a few submitter workflows:

1. Tested out the dev-gui and was able to interact with everything and submit jobs with no issue
2. Installed PySide2 with the gui and it behaved the exact same way as PySide6
3. Used it as a local dependency within Maya and Nuke and confirmed that it all still worked with no issue

I then performed manual testing around the installation workflow when a user doesn't have the optional gui dependencies available

1. When using python with `pip install deadline[gui], confirmed that I was able to use the gui-submit option for job bundles.
2. When using python with pip install deadline, confirmed that it prompted me to install PySide6. Subsequent launches did not ask me, as the dependencies were available.
3. When using the deadline executable from pyinstaller, confirmed that it prompted me to install PySide6 using the python available on my path. Subsequent launches did not ask me, as the dependencies were available.
4. When using the deadline executable from pyinstaller AND without having python3 or python on the path, confirmed that it prompted me to install and gave me a command that I could manually run with a python install that worked. Subsequent launches did not ask me, as the dependencies were available.

Optional GUI components for deadline are unavailable. Would you like to install PySide? [y/N]: y
Unable to install GUI dependencies, if you have python available you can install it by running:

	python -m pip install 'PySide6-essentials==6.6.*' --python-version 3.10 --only-binary=:all: -t /Users/epmog/deadline-cloud/deadline_pyinstaller/cli

deadline-cloud epmog$

Was this change documented?

N/A

Is this a breaking change?

No, all applications should continue to work since deadline now brings in qtpy by default (without any of the actual GUI deps)

[ddneilson]

I'm really looking forward to being able to use this!

[marofke]

This is awesome! My local workspace wasn't working with GUI stuff after upgrading my python version, but this got it working again after I pulled these changes locally.

Very slick experience to call:

deadline bundle gui-submit --browse

Have it prompt me to install pyside, and then continue with opening my file explorer to do the gui submit.