PY-22406: Report unittest as subtests

* Some issues are still missed (see my comments in issue)
* EnvTagsRequired now can be applied to method

python/testData/testRunner/env/unit/test_subtest.py

@@ -0,0 +1,9 @@
+from unittest import TestCase
+
+
+class SpamTest(TestCase):
+    def test_test(self):
+        for i in range(0, 10):
+            with self.subTest(i=i):
+                print(1)
+                self.assertTrue(i % 2)