Class `APIKey` is overloaded

[haakonvt]

The SDK defines two classes with name APIKey:

# In cognite/client/credentials.py
class APIKey(CredentialProvider):
# In cognite/client/data_classes/iam.py
class APIKey(CogniteResource):

I guess this could lead to confusion.

[haakonvt]

Solved by #1201