This updates the pipe library to use generics for the request payload
and the status value. This allows the solver to put in explicit types
rather than rely on type casting from interfaces which helps with type
safety and understandability.
The status value used by the solver uses the `any` type instead of an
explicit type because the `unpark` method takes a generic list of pipes
and the different pipes have different result types. We can likely
change this in the future or create a discriminated union for the
types that can be used in this package. That is left for future work
because at least the request payload is typed now.
Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>
