inspect.signature() raises TypeError for non-comparable callable

# Bug report

Example:
```py
class NoncomparableCallable:
    def __call__(self, a):
        pass
    def __eq__(self, other):
        1/0

import inspect
inspect.signature(NoncomparableCallable())
```
Real world example -- the result of `functools.cmp_to_key()` (see also #118402).



### Linked PRs
* gh-118405
* gh-118424