Revisit core, main and foundation integration tests

[ppalaga]

Things to improve:

• Minimize the dependencies (timer, log might get removed from the core test)
• Consider splitting some of the modules to Increase isolation, e.g. timer, and log do not have their isolated modules
• Consider introducing a grouped test to execute all modules at once on the CI
• Make sure we have both consumer and producer assertions for direct

[JiriOndrusek]

@ppalaga I'd like to be sure, that I understand this issue correctly:

• We should try to create separate test modules for e.g. log, timer and therefore remove this dependencies from core test
• We should verify that producer and consumer cases are tested for direct
• I probably don't understand what does grouped test mean in this case - do you mean to introduce grouped test, which will contain core tests and these separated ones (like timer, log, ..)?