bpo-37177: make IDLE's search dialogs transient (GH-13869)

This avoids the search dialogs being hidden behind the editor window.
(cherry picked from commit 554450fb4e)

Co-authored-by: Tal Einat <taleinat@gmail.com>

Lib/idlelib/searchbase.py

@@ -54,6 +54,7 @@ class SearchDialogBase:
         else:
             self.top.deiconify()
             self.top.tkraise()
+        self.top.transient(text.winfo_toplevel())
         if searchphrase:
             self.ent.delete(0,"end")
             self.ent.insert("end",searchphrase)
@@ -66,6 +67,7 @@ class SearchDialogBase:
         "Put dialog away for later use."
         if self.top:
             self.top.grab_release()
+            self.top.transient('')
             self.top.withdraw()
 
     def create_widgets(self):