polynomial: Add basic ops (#89525)

Adds a few basic polynomial ops.

- add, sub, mul
- mul_scalar
- leading_term, monomial_mul, monomial (useful for lowering `mul` to
standard MLIR)
- from_tensor, to_tensor, constant

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Co-authored-by: Jeremy Kun <j2kun@users.noreply.github.com>
Co-authored-by: Oleksandr "Alex" Zinenko <ftynse@gmail.com>