majorly refactor collection process

- get rid of py.test.collect.Directory alltogether.
- introduce direct node.nodeid attribute
- remove now superflous attributes on collect and test reports

testing/plugin/test_runner.py

@@ -257,9 +257,9 @@ class TestCollectionReports:
         assert not rep.skipped
         assert rep.passed
         locinfo = rep.location
-        assert locinfo[0] == col.fspath
+        assert locinfo[0] == col.fspath.basename
         assert not locinfo[1]
-        assert locinfo[2] == col.fspath
+        assert locinfo[2] == col.fspath.basename
         res = rep.result
         assert len(res) == 2
         assert res[0].name == "test_func1"