Add Lifecycle Rule Property Setters

From: https://github.com/googleapis/python-storage/pull/199#discussion_r478512169

Object Lifecycle Management Rules don't have property setters and requires using the class constructor in this case. 

This is a FR in case we want to introduce setters. This isn't prioritized at the moment and waiting for more user feedback.