[llvm] [flang][runtime] Allow some list-directed child output to advance (PR #166847)

[Peter Klausler via llvm-commits]

klausler wrote:

So the extension is to interpret an array constructor with no explicit type-spec as having the dynamic type of its elements, not their common declared type, when the elements are polymorphic?  And this is independent of the context -- it is not peculiar to `SOURCE=` specifiers in `ALLOCATE` statements?

https://github.com/llvm/llvm-project/pull/166847