[ty] Add property test generators for variable-length tuples (#18901)
Add property test generators for the new variable-length tuples. This
covers homogeneous tuples as well.
The property tests did their job! This identified several fixes we
needed to make to various type property methods.
cf https://github.com/astral-sh/ruff/pull/18600#issuecomment-2993764471
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Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>