IDLE: Switch search dialogs to ttk widgets, and other refinement

GitHub fields:

assignee = 'https://github.com/terryjreedy'
closed_at = None
created_at = <Date 2016-07-10.20:19:37.524>
labels = ['3.8', 'expert-IDLE', 'type-feature', '3.7']
title = 'IDLE: Switch search dialogs to ttk widgets, and other refinement'
updated_at = <Date 2021-01-22.08:27:50.787>
user = 'https://github.com/terryjreedy'

bugs.python.org fields:

activity = <Date 2021-01-22.08:27:50.787>
actor = 'terry.reedy'
assignee = 'terry.reedy'
closed = False
closed_date = None
closer = None
components = ['IDLE']
creation = <Date 2016-07-10.20:19:37.524>
creator = 'terry.reedy'
dependencies = ['33987']
files = ['43680', '43968']
hgrepos = []
issue_num = 27477
keywords = ['patch']
message_count = 9.0
messages = ['270131', '270141', '271653', '271752', '271791', '320804', '375094', '379302', '385484']
nosy_count = 3.0
nosy_names = ['terry.reedy', 'markroseman', 'python-dev']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue27477'
versions = ['Python 3.7', 'Python 3.8']