Allow for multi-function coding problems

Instead of only testing one function per question, let's build a higher difficulty problem set that requires students to use multiple functions to solve it. Instead of just testing one function again one set of io, let's do an arbitrary length (with corresponding test suites.)

A workaround has already been established. Both autograded tests from SF (F24) had problems that asked users to copy and paste solutions from a previous problem into a subsequent problem. These problems involved writing different list sorting implementations, which is a good problem for something like this. Similarly, we could make problems that culminate in making card games :D like uno, 31, poker?