Add a function to lookup all things with the same top tycon in a TypeMap
Add a function to get all inert fun-eqs for the given tycon.
Hook-in built-in interactions with inerts.

After the solver extracts its relevant constraints
(i.e., function applications where the head match),
we check for any additional functional equation constraints for the
same built-in function.  Then, we call out to the custom
interaction, to collect some extra derived constraints.
Add some simple interactions with inerts for (+), (*), and (^).