AP_STACK ignores stack contents

[bgamari]

We will miss many pointers due to the fact that heap_view_closurePtrs considers a AP_STACK closures to have only a single pointer to the applied function.

[mpickering]

GHC issue - https://gitlab.haskell.org/ghc/ghc/issues/15375

[mpickering]

We have everything we need now to decode such information in ghc-debug I think.