Consistently add exist_ok / missing_ok parameters to directory creation/deletion functions

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-09-16.22:45:09.217>
labels = ['type-feature', 'library', '3.9']
title = 'Consistently add exist_ok / missing_ok parameters to directory creation/deletion functions'
updated_at = <Date 2019-10-16.18:13:23.496>
user = 'https://github.com/timhoffm'

bugs.python.org fields:

activity = <Date 2019-10-16.18:13:23.496>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-09-16.22:45:09.217>
creator = 'timhoffm'
dependencies = []
files = []
hgrepos = []
issue_num = 38194
keywords = []
message_count = 3.0
messages = ['352590', '354800', '354809']
nosy_count = 3.0
nosy_names = ['serhiy.storchaka', 'valorien', 'timhoffm']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue38194'
versions = ['Python 3.9']