urllib.parse.*Result: support _replace for additional computed addresses

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-03-24.22:05:29.911>
labels = ['3.8', 'type-feature', 'library']
title = 'urllib.parse.*Result: support _replace for additional computed addresses'
updated_at = <Date 2019-03-27.13:46:03.747>
user = 'https://github.com/csabella'

bugs.python.org fields:

activity = <Date 2019-03-27.13:46:03.747>
actor = 'fdrake'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-03-24.22:05:29.911>
creator = 'cheryl.sabella'
dependencies = []
files = []
hgrepos = []
issue_num = 36418
keywords = []
message_count = 1.0
messages = ['338762']
nosy_count = 2.0
nosy_names = ['fdrake', 'cheryl.sabella']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue36418'
versions = ['Python 3.8']