Add `Equation` struct, and new default methods to `PolynomialCommitment` trait for opening and checking proofs of equation satisfaction

* Unifies `SinglePolynomialCommitment` and `MultiPolynomialCommitment` under a single trait `PolynomialCommitment`. This latter trait now handles committing to multiple polynomials at once, and evaluating them at a point or at a queryset.
* Changes the setup method to output a new UniversalParams associated type that is specialized by a new trim method that allows users to specify the maximum degree of polynomial that they'd like to support, along with the degree bounds they'd like to enforce, outputs specialized ck and vk structs that work only for these degree bounds and supported degree.

* Finally, `open` and `check` now produce and check proofs of evaluation for a list of polynomials at a single point, while `batch_open` and `batch_check` do the same for `QuerySet`s.

* Separates KZG10 into a standalone construction that can be used in a whitebox manner to construct a Sonic style PC in the future.

* Fixes and unifies test infrastructure.

Consolidate MultiPC API around LabeledPolynomials