Add race-free os.link and os.symlink wrapper / helper

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-04-18.08:44:47.900>
labels = ['type-feature', 'library', '3.9']
title = 'Add race-free os.link and os.symlink wrapper / helper'
updated_at = <Date 2021-05-01.15:06:22.654>
user = 'https://github.com/HaleTom'

bugs.python.org fields:

activity = <Date 2021-05-01.15:06:22.654>
actor = 'Yonatan Goldschmidt'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-04-18.08:44:47.900>
creator = 'Tom Hale'
dependencies = []
files = []
hgrepos = []
issue_num = 36656
keywords = ['patch']
message_count = 16.0
messages = ['340474', '340526', '340546', '341373', '341376', '341753', '342434', '344408', '344501', '344575', '344911', '344915', '346717', '346882', '372450', '383968']
nosy_count = 8.0
nosy_names = ['taleinat', 'rbcollins', 'a.badger', 'serhiy.storchaka', 'eryksun', 'Michael.Felt', 'Tom Hale', 'Yonatan Goldschmidt']
pr_nums = ['14464']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue36656'
versions = ['Python 3.9']