Automatically set parent thread idents on thread start

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-12-03.09:49:23.451>
labels = ['3.9', '3.10']
title = 'Automatically set parent thread idents on thread start'
updated_at = <Date 2020-12-03.09:49:23.451>
user = 'https://github.com/gaborbernat'

bugs.python.org fields:

activity = <Date 2020-12-03.09:49:23.451>
actor = 'gaborjbernat'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2020-12-03.09:49:23.451>
creator = 'gaborjbernat'
dependencies = []
files = []
hgrepos = []
issue_num = 42552
keywords = []
message_count = 1.0
messages = ['382398']
nosy_count = 1.0
nosy_names = ['gaborjbernat']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue42552'
versions = ['Python 3.9', 'Python 3.10']