refactor: remove superfluous type parameters

[Daniel-Aaron-Bloom]

Many types and functions use generics with parameters like:

F: RichField + Extendable<D>, C: GenericConfig<D, F = F>

Instead, those places could use C: GenericConfig<D>, substituting C::F in place of F where necessary.

PackedField is a similar story.

Removing these parameters can simplify type declarations and turbofishes for downstream crates.