PySide6 refactor

[twizmwazin]

Instructions to test:

1. Set up an angr-dev environment as normal.
2. Install the master branch of https://github.com/angr/pyqodeng to your environment.
3. Install this branch.
4. Enjoy!

[github-actions]

Unit Test Results

5 tests  ±0   5 ✔️ ±0   17s ⏱️ -1s
5 suites ±0   0 💤 ±0 
5 files   ±0   0 ❌ ±0 

Results for commit fef365d. ± Comparison against base commit 9cb5574.

♻️ This comment has been updated with latest results.

[twizmwazin]

So this seems like it was even less work than I was thinking. There are still issues, mostly in pyqodeng, but as far as I can tell the UI otherwise works. Would people be able to give this a go and see if they can find issues?

[ltfish]

Currently fails on PySide6 6.4 because of the following issues:

• https://bugreports.qt.io/browse/PYSIDE-2088
• Don't re-assign Qt.MouseButton.MiddleButton on PySide6 spyder-ide/qtpy#374

[ltfish]

I'm going to merge this branch to master as soon as CI passes.

[ltfish]

Currently fails on PySide6 6.4 because of the following issues:

* https://bugreports.qt.io/browse/PYSIDE-2088

* [Don't re-assign Qt.MouseButton.MiddleButton on PySide6 spyder-ide/qtpy#374](https://github.com/spyder-ide/qtpy/pull/374)

Both issues have been fixed. We can move to PySide6 6.4.x once qtpy and PySide6 release new versions to PyPI.