Expand the GC hole fix for explicitly initialized structs (#69501)

Expand the GC hole fix for explicitly initialized structs (#69501)

* Expand the fix for explicitly initialized structs

Liveness code already recognizes that it cannot delete certain local
stores with the implicit side effect of "explicit initialization".

However, it was only doing that for indirect "InitBlk" forms, while
the store can have more or less arbitrary shape (the only requirement
is that is must be "entire").

Fix this by not constraining the check to "InitBlk"s.

* Add a test