fix: get_object dynamic supports methods set by assignments

[machow]

This PR allows for dynamically documenting methods defined like...

from some_module import some_func

class SomeClass:
    some_method = some_func

I refactored the approach we use to look for the canonical path to an object. Previously, it wasn't always finding where the dynamic objects lived, and so resulted in returning something closer to the static result. This means that in the above case it believed some_method was an attribute.

I moved the logic for looking for where an object lives into _canonical_path, so hopefully it is easier to add and test new cases.