IDLE - Move help_url code to a help module function

[terryjreedy]

editor.EditorWindow.__init__ lines 79 to 114 should be refactored a bit and moved to a module level function in help.py.

Do this after #95841 is complete.

Linked PRs

• gh-95844: Move help_url code to a help module function #129971
• [3.14] gh-95844: Move help_url code to a help module function (GH-129971) #138484
• [3.13] gh-95844: Move help_url code to a help module function (GH-129971) #138485