Multiple consistency fixes. Submitting in one change to make sure they work well together.

Ensure consistency of handling bound methods between autograph and tf.function. Fix the detection of wrapt used on methods. Fix rewrap to consistently replace the target function even if it was not a decorator.
This is a resubmission of the previous change with the same name. Difference from previous: covers the case when a wrapt-decorated method is converted independently, rather than being annotated. See the two new tests in user_decorators_test for details.

PiperOrigin-RevId: 235782711