Update python repl examples to match current code

[andy31415]

https://github.com/project-chip/connectedhomeip/tree/master/docs/guides/repl

contains some repl examples. This seems to need updating:

• it relies that import chip.clusters as Clusters is done (like our py examples). Need to update the files to make them clearer
• uses pkgutil.get_loader which is deprecated and scheduled for removal: https://docs.python.org/3/library/pkgutil.html#pkgutil.find_loader

Also may need some updates in examples for commissioning. Expect to:

• fix up includes (maybe clusters should be pre-included in the init script, with tags for our linter to not complain)
• replace get_loader usage
• validate examples (especially commissioning) to make sure they are usable