Add a way to hide fields in dataclasses

GitHub fields:

assignee = 'https://github.com/ericvsmith'
closed_at = None
created_at = <Date 2021-10-12.15:23:21.079>
labels = ['type-feature', '3.11']
title = 'Add a way to hide fields in dataclasses'
updated_at = <Date 2021-10-13.16:12:44.238>
user = 'https://bugs.python.org/formigacomcaimbra'

bugs.python.org fields:

activity = <Date 2021-10-13.16:12:44.238>
actor = 'eric.smith'
assignee = 'eric.smith'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2021-10-12.15:23:21.079>
creator = 'formigacomcaimbra'
dependencies = []
files = []
hgrepos = []
issue_num = 45446
keywords = ['patch']
message_count = 3.0
messages = ['403749', '403756', '403845']
nosy_count = 3.0
nosy_names = ['eric.smith', 'python-dev', 'formigacomcaimbra']
pr_nums = ['28904']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue45446'
versions = ['Python 3.11']