[flang] Fix fir::isPolymorphic for TYPE(*) assumed-size arrays (#77339)

fir::isPolymorphic was returning false for TYPE(*) assumed-size arrays
causing bad fir.rebox to be created when passing a polymorphic actual
argument to such TYPE(*) dummy.

Fix fir::isAssumedSize to return true for fir.ref<fir.array<none>> and
fir.ref<none>.

@cabreraam, I found this bug when testing your patch, although it is not
caused by it, so you may hit it when passing TYPE(*) deferred shape of
to assumed size TYPE(*) with a different rank.