test: validate illegal method-variation calls

[matosys]

Currently there are no tests, that validates the usage of method-variation calls within fixtures.

Since it is unclear, which method variation is active inside session, setup and scenario fixtures, the test should check if it is possible to use the correct method variations inside variation or testcase fixtures and also secure that a runtime-error is thrown for using method-variations inside session, setup and scenario fixtures.

The tests should be provided for fixtures inside Scenario and Setup classes.