Verify all examples work with Python 3.11

[dpinte]

• [ ] verify all examples in https://github.com/enthought/chaco/tree/main/examples run as expected. As those are not unit tests, they need to be executed manually. Analysing the stdout/stderr might be imporant to capture potential trait errors, etc. that the UI would not expose
• [ ] check the integration with etsdemo tool (see traitsui)