Consider always keeping the cassette with default name

[Stranger6667]

For example if there are a test and a cassette for it and then we need to add some common data:

@pytest.mark.vcr("extra.yaml")
def test_something():
    pass

In this case, we will look only into extra.yaml because of this - https://github.com/kiwicom/pytest-recording/blob/master/src/pytest_recording/plugin.py#L84

However, it is useful to be able to add some extra common data and still using some specific cassette for the test (named by the default rules). Now it is possible only with specifying it manually in the vcr mark