* Core: fix settings API for removal of Python 3.8, 3.9
This is fixing 2 problems:
- The `World` class has the annotation:
`settings: ClassVar[Optional["Group"]]`
so `MyWorld.settings` should not raise an exception like it does for some worlds.
With the `Optional` there, it looks like it should return `None` for the worlds that don't use it. So that's what I changed it to.
- `Group.update` had some code that required `typing.Union` instead of the Python 3.10 `|` for unions.
added unit test for this fix
added change in Zillion that I used to discover this problem and used it to test the test
* fix copy-pasted stuff
* tuple instead of set
Co-authored-by: black-sliver <59490463+black-sliver@users.noreply.github.com>
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Co-authored-by: black-sliver <59490463+black-sliver@users.noreply.github.com>
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