extract FStar.Universe to krml as identity
extract FStar.Universe to krml as identity

@nikswamy initially suggested to add some rules into
FStar.Extraction.Krml to extract FStar.Universe (without
delving into the details.) This solution here seems to work
well, and it also works around FStarLang/karamel#268 for array
operations: by virtue of removing the inner tuple below
`ptr`, array types now extract to `t *` instead
of `K___t___`

FStarLang/FStar,FStarLang/FStar,FStarLang/FStar