Extensible Shape dispatch.

Presently, supporting a new shape requires defining a new `ContactDispatcher`, which is boilerplate-heavy, awkward to compose, and does not account for CCD or high-level query functions. This could be improved by relying something like on one or more dynamic containers that map `(TypeId, TypeId) -> T` for various query functions `T`, and which can easily be mutated by the user to add new cases. However, implementation of some queries in terms of abstract interfaces like `&dyn SupportMap` complicates this as the desired algorithm is associated with an unbounded set of concrete `TypeId`s.