Improvements in QA tests code

Description

Sorry for not following template strictly. This is a suggestion/wishlist based on inspecting the code rather than behavior.

Project code under /qa subdirectory is not structured very well. Preferably there should be tendency to add tests to existing test applications, instead of creating new, small ones.

During my development I created some integration tests and they are very handy: https://gitlab.com/kicad/code/kicad/-/blob/0bedfdbf8d01c9345f2f1a12eaad72f0bae89032/qa/eeschema/sim/test_cursor.cpp

I believe there will be more and more of them (according to roadmap) so it's worth to prepare the ground. Threads below will contain some findings where discussion can take place.

KiCad Version

Findings below are based on commit: de66c65f