bpo-43013: Fix old tkinter module names in idlelib (GH-24326)

Lowercase 'tkColorChooser', 'tkFileDialog', 'tkSimpleDialog', and
'tkMessageBox' and remove 'tk'.  Just lowercase 'tkFont' as 'font'
is already used.  Adjust import.
diff --git a/Lib/idlelib/squeezer.py b/Lib/idlelib/squeezer.py
index be1538a..3046d80 100644
--- a/Lib/idlelib/squeezer.py
+++ b/Lib/idlelib/squeezer.py
@@ -17,7 +17,7 @@
 import re
 
 import tkinter as tk
-import tkinter.messagebox as tkMessageBox
+from tkinter import messagebox
 
 from idlelib.config import idleConf
 from idlelib.textview import view_text
@@ -147,7 +147,7 @@ def expand(self, event=None):
         if self.is_dangerous is None:
             self.set_is_dangerous()
         if self.is_dangerous:
-            confirm = tkMessageBox.askokcancel(
+            confirm = messagebox.askokcancel(
                 title="Expand huge output?",
                 message="\n\n".join([
                     "The squeezed output is very long: %d lines, %d chars.",
@@ -155,7 +155,7 @@ def expand(self, event=None):
                     "It is recommended to view or copy the output instead.",
                     "Really expand?"
                 ]) % (self.numoflines, len(self.s)),
-                default=tkMessageBox.CANCEL,
+                default=messagebox.CANCEL,
                 parent=self.text)
             if not confirm:
                 return "break"