plistlib should export UIDs in XML like Apple does

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-02-23.14:23:39.410>
labels = ['type-feature', 'library', '3.9']
title = 'plistlib should export UIDs in XML like Apple does'
updated_at = <Date 2020-11-27.20:19:52.873>
user = 'https://github.com/Artoria2e5'

bugs.python.org fields:

activity = <Date 2020-11-27.20:19:52.873>
actor = 'bigfootjon'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-02-23.14:23:39.410>
creator = 'Artoria2e5'
dependencies = []
files = []
hgrepos = []
issue_num = 39732
keywords = ['patch']
message_count = 1.0
messages = ['362513']
nosy_count = 5.0
nosy_names = ['ronaldoussoren', 'ned.deily', 'serhiy.storchaka', 'Artoria2e5', 'bigfootjon']
pr_nums = ['18622']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue39732'
versions = ['Python 3.9']