Issue #10291: Backport 004fe3449193 with a few changes due to 22095.
Will forward port 22095 changes separately.
Issue #10291: null merge
Issue #22065: forward port the changes in c26862955342, update docstring with
changes that were only merged into demohelp.txt, and re-delete demohelp.txt.
Issue #22065: Try the delete demohelp.txt part again.
#22053: actually remove .txt files from 3.4.
Null merge.
Issue #22065: Update turtledemo menu creation; don't use obsolete Menubutton.
Merge with 3.4