Type of enum value being incorrectly inferred

**Note**: this content is roughly equivalent to that of an still unanswered [question I posted at SO](https://stackoverflow.com/questions/59829094/incorrect-inference-of-enum-values-type-with-astroid-the-engine-behind-py).

``` py
from enum import Enum

class Whatever(Enum):
Foo = 1
Bar = 2

def f():
x = Whatever.Foo
```

Consider the program above an a call to `infer()` on expression `Whatever.Foo`.

### Current behavior
I get a (proxied) `ClassDef` for a `Foo` "type".

### Expected behavior
I'd expect a (proxied) `ClassDef` for `Whatever`.

This would be according to the [language specification](https://docs.python.org/3/library/enum.html#creating-an-enum), that says that *the type of an enumeration member is the enumeration it belongs to.*

astroid version: 2.3.3

Start by reproducing the supplied Enum example with astroid 2.3.3 and inspect inference for the Whatever.Foo expression. Compare the current proxied ClassDef for Foo with the expected proxied ClassDef for Whatever; done means enum-member inference reports the containing enum type.

Written by the indexing model from the issue text.