run-tests: create classes for representing tests Currently, the state for an individual test is scattered across a number of functions and variables. This patch begins a process of isolating a single test's state into instances of a class. It does this by establishing a new Test base class and child classes for Python tests and T tests. The class currently has a run() API that proxies into the existing "runner" functions. Upcoming patches will move the logic for each test type into the class.