Improve the IDLE shell save command

GitHub fields:

assignee = 'https://github.com/terryjreedy'
closed_at = None
created_at = <Date 2021-09-27.00:28:07.219>
labels = ['expert-IDLE', 'type-feature', '3.11']
title = 'Improve the IDLE shell save command'
updated_at = <Date 2022-03-20.22:25:42.712>
user = 'https://github.com/stevendaprano'

bugs.python.org fields:

activity = <Date 2022-03-20.22:25:42.712>
actor = 'steven.daprano'
assignee = 'terry.reedy'
closed = False
closed_date = None
closer = None
components = ['IDLE']
creation = <Date 2021-09-27.00:28:07.219>
creator = 'steven.daprano'
dependencies = []
files = []
hgrepos = []
issue_num = 45297
keywords = []
message_count = 2.0
messages = ['402686', '415638']
nosy_count = 2.0
nosy_names = ['terry.reedy', 'steven.daprano']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue45297'
versions = ['Python 3.11']