fix(pytest): properly include nested classes in fullName, historyId, testCaseId, and subSuite

[delatrie]

Context

Pytest supports nested test classes:

class TestFoo: class TestBar: def test_baz(self): pass

Currently, Allure Pytest incorrectly assumes there is zero or one test class in every given nodeid when calculating fullName and subSuite. Since the test above has nodeid module_test.py::TestFoo::TestBar::test_baz, the calculations become invalid.

Given that testCaseId and historyId depend on fullName, these properties are calculated incorrectly as well.

The PR fixes how Allure Pytest handles such cases:

• All test classes are now included in fullName (joined with .).
• All test classes are now included in the value of the subSuite label (joined with >).

Fixes #868.

Checklist

• Sign Allure CLA
• Provide unit tests