Refactor to drop dependency on decorator package

[jennifer-richards]

Description

We have a few decorators defined in ietf/utils/decorator.py that use the "decorator" package. This provides the @decorator decorator and a decorate method. The built-in Python functools.wraps() method can fulfill the needs here without the additional dependency. As far as I can tell we're not making use of any of the features provided by the "decorator" package.

The @decorator mechanism also seems to interfere with Django's @method_decorator, which led to refactoring the requires_api_key decorator already.

Code of Conduct

• I agree to follow the IETF's Code of Conduct

[jennifer-richards]

Reopening - there is still a dependency in debug.py as @microamp mentioned in his PR comment