Adjust DrRacket to not use on-demand to populate the teachpack menu.
Adjust DrRacket to not use on-demand to populate the
teachpack menu.

Instead DrRacket explicitly changes the menu items when
the language changes or when a teachpack is added/removed

Also, Rackety.

Closes PR 13395

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket