Issues pickling sympy.Function('f')

We have a test failure in our SymPy test suite from cloudpickle. I have bisected it to the cloudpickle commit https://github.com/cloudpipe/cloudpickle/commit/aec80d21ddff84cf2a83dce3cb5921a9f58ffd05

The failure is described at https://github.com/sympy/sympy/issues/15116

The basic failure is this:

```py
>>> import cloudpickle
>>> from sympy import Function
>>> f = Function('f')
>>> f1 = cloudpickle.loads(cloudpickle.dumps(f))
>>> f.__dict__['_prop_handler']
{'commutative': , 'negative': , 'positive': , 'complex': }
>>> f1.__dict__['_prop_handler']
{'commutative': , 'negative': , 'positive': , 'complex': }
>>> from sympy import Expr
>>> Expr._eval_is_negative

```

The SymPy test tests that all the attributes are the same, and fails because cloudpickle creates new instances of the Expr methods.

I'm not clear if this affects functionality or not.

CC @ssanderson