Issue 13404 - heap-allocating a struct passes TypeInfo_Pointer to the GC, not TypeInfo_struct

https://issues.dlang.org/show_bug.cgi?id=13404

When allocating a struct with "new", do not pass the pointer type info to the runtime, but the struct type info.

This PR needs https://github.com/D-Programming-Language/druntime/pull/941 to be merged at the same time.