Refactor tests structure

Move all the render test utility methods to a separate class and leave
only tests in RenderTests class (old Main).
The idea is to improve the organization to allow to create a set of
performance tests and also to allow the tests to grow more structured.

Test: Just moved tests around
Change-Id: I3b773d0745700dd2a52f937b9b668a2d374b8686
5 files changed