#2317353 Conditions tests refactoring

Ticket: 2317353 - RulesIntegrationTestBase + tests are using setContextValue() incorrectly

I have ported all the condition tests to the RulesIntegrationTest class and did some little refactorings around, such as separating Unit and Integration tests, renamed the base testcase classes to match PHPUnit's convention (*TestBase to *TestCase). I haven't looked at the Context Values yet as I am not sure if they have been fully fixed in Ticket 2346659.
RulesIntegrationTestBase is named intentionally that way, because it is just an abstract base class and not an actual test case. That's how we differentiate between actual tests and helper test base classes.