Add regression tests for Enum.name and .value inference

Ref pylint-dev#1932. Ref pylint-dev#2062. Ref pylint-dev/astroid#1020.

Author: nelfin

tests/functional/e/enum_subclasses.py

@@ -0,0 +1,19 @@
+# pylint: disable=missing-docstring
+from enum import Enum, IntEnum
+
+
+class Issue1932(IntEnum):
+    """https://github.com/PyCQA/pylint/issues/1932"""
+    FOO = 1
+
+    def whats_my_name(self):
+        return self.name.lower()
+
+
+class Issue2062(Enum):
+    """https://github.com/PyCQA/pylint/issues/2062"""
+    FOO = 1
+    BAR = 2
+
+    def __str__(self):
+        return self.name.lower()