Class usage came from the unittest framework and it was always redundant
after migration to the pytest. This commit removes classes from files
containing tests to make them more readable and understandable.
Prerequisites check moved to the module level to simplify class structure.
Discovery and prerequisites checks functions moved to the separate files.
Introduced "require" fixture to provide per-test requirements check.
Common methods from applications/proto.py converted to the fixtures.
sysctl check moved to the specific file where it is using.
Some options moved to the constructor to have early access.
Added "go" availability check before trying to build an application.
update_action() method used were possible and fixed bug with
the relative path determination in test_static_chroot.py.
Templates optimization and style fixes.
Introducing "unit.log.Log" class for "unit.log" file management.
Moving "findall()" function into TestApplicationProto.
Using "os.kill()" to send signals.
