[compiler] listServices should take in namespace

[iscai-msft]

Currently, listServices can only be called from a program instance. This doesn't work well if we're doing mutation, because if we want to just mutate the global namespace once, then find all of the services in the program, we aren't able to explicitly tell listServices to iterate over our specific mutated global namespace.

It would be great if listServices could also take in an optional specific namespace, allowing you to find all services associated with a given namespace. This could be a good typekit too as a different implementation way