Update embedding examples

[jacobwilliams]

The internal_ipkernel.py and ipkernel_qtapp.py are out of date. Some issues:

• It is using PyQt4, which is very old, and not supported on some platforms (e.g. osx-arm64)
• Explicit use of PyQt means it doesn't work with PySide. Should use qtpy so it will work with Pyside2/6 or PyQt5/6.
• This line: from IPython.lib.kernel import connect_qtconsole fails on recent ipythons. I think the replacement is from ipykernel import connect_qtconsole. See ModuleNotFoundError: No module named 'IPython.lib.kernel' ipython#13610
• The connect calls also would need to be updated (I think those are the old style signals).