[ty] Make `TrackedConstraintSet` interned (#22545)
Using tracked struct in cyclic queries is [broken in
Salsa](https://github.com/astral-sh/ruff/pull/22537#issuecomment-3740749611).
This PR updates `TrackedConstraintSet` to be interned instead.
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Co-authored-by: Douglas Creager <dcreager@dcreager.net>
