I'm writing this patch for two purposes:

1. I want to reduce the number of times `object_id` is called.  Calling
   `object_id` can have negative impacts on performance in Ruby 2.7+, so
   it would be nice to stop calling it.

2. I'm not sure why we're treating lambdas specially here.  It looks
   like we wanted to prevent people from skipping callbacks that were
   defined with a lambda, but I think that is silly.  If the user has a
   reference to a lambda, and they want to skip it, we should let them.

I think this cleans up some code, helps with performance, and is a more
intuitive interface.