Add a polynomial dialect shell, attributes, and types (#72081)

RFC:
https://discourse.llvm.org/t/rfc-a-poly-dialect-for-polynomial-arithmetic/73891



This PR implements the minimal work needed to represent the polynomial
type such that it can be tested with `lit`.

In this PR:

- Dialect shell
- `Polynomial` data structure needed for folding
- Polynomial attributes (`PolynomialAttr` and `RingAttr` which store a polynomial)
- `polynomial.polynomial` type
- Basic lit tests

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Co-authored-by: Jeremy Kun <j2kun@users.noreply.github.com>