When adjusting the existing tests, I aimed to avoid dealing with the
special case in other tests if it's not necessary to do so (that is,
avoid using `float` and `complex` as examples where we just need "some
type"), and keep the tests for the special case mostly collected in the
mdtest dedicated to that purpose.
Fixes https://github.com/astral-sh/ruff/issues/14932
Fix#14498
## Summary
This PR adds `typing.Union` support
## Test Plan
I created new tests in mdtest.
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Co-authored-by: Carl Meyer <carl@astral.sh>