fix auditlog refs

[seanpreston]

IPython 8.3.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]: from fidesops.db.session import get_db_session
In [2]: from fidesops.models.privacy_request import PrivacyRequest
In [3]: db = get_db_session()()
In [4]: PrivacyRequest.all(db)

The above results in the following error:

NameError: name 'AuditLog' is not defined
...
InvalidRequestError: When initializing mapper mapped class PrivacyRequest->privacyrequest, expression 'foreign(AuditLog.privacy_request_id)==PrivacyRequest.id' failed to locate a name ("name 'AuditLog' is not defined"). If this is a class name, consider adding this relationship() to the <class 'fidesops.models.privacy_request.PrivacyRequest'> class after both dependent classes have been defined.

because we're referring to AuditLog on the PrivacyRequest model via "AuditLog", which requires the class to be present in local scope, instead of using the imported class.

This PR also adds FidesopsUser.audit_logs to link FidesopsUser instances in the same way as PrivacyRequests.