## Summary
Fixes https://github.com/astral-sh/ruff/issues/18602 by:
1. Avoiding a fix when `*args` are present
2. Inserting the `Generic` base class right before the first keyword
argument, if one is present
In an intermediate commit, I also had special handling to avoid a fix in
the `**kwargs` case, but this is treated (roughly) as a normal keyword,
and I believe handling it properly falls out of the other keyword fix.
I also updated the `add_argument` utility function to insert new
arguments right before the keyword argument list instead of at the very
end of the argument list. This changed a couple of snapshots unrelated
to `PYI059`, but there shouldn't be any functional changes to other
rules because all other calls to `add_argument` were adding a keyword
argument anyway.
## Test Plan
Existing PYI059 cases, plus new tests based on the issue
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Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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