fix(deprecation): stacked decorators breaks getting the real callable __name__ attribute
This is yet another impossible deep magic bug.
Normally the test and the docstring should explain it all. Don't hesitate to ask if you have questions.
If it's merged I'll backport it on 1.7 (I didn't do the "put on 1.7 then merge into default" because branches have diverged a bit too much due to typing and stuff)