Convert importlib.abc to use typing.Protocol

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-11-12.22:47:40.242>
labels = ['type-feature', 'library', '3.9']
title = 'Convert importlib.abc to use typing.Protocol'
updated_at = <Date 2021-10-20.21:07:21.258>
user = 'https://github.com/brettcannon'

bugs.python.org fields:

activity = <Date 2021-10-20.21:07:21.258>
actor = 'barry'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-11-12.22:47:40.242>
creator = 'brett.cannon'
dependencies = []
files = []
hgrepos = []
issue_num = 38782
keywords = ['patch']
message_count = 1.0
messages = ['356501']
nosy_count = 5.0
nosy_names = ['barry', 'brett.cannon', 'levkivskyi', 'ZackerySpytz', 'nanjekyejoannah']
pr_nums = ['21245']
priority = 'low'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue38782'
versions = ['Python 3.9']