[kernel] Run global constructors

Look up the global constructor list that the linker outputs, and run
them all. Required creation of the `kutil::no_construct` template for
objects that are constructed before the global constructors are run.

Also split the `memory_initialize` function into two - one for just
those objects that need to happen before the global ctors, and one
after.

Tags: memory c++

src/kernel/objects/kobject.cpp

@@ -1,11 +1,8 @@
 #include "j6/errors.h"
 #include "j6/signals.h"
 #include "j6/types.h"
-#include "kutil/heap_allocator.h"
 #include "objects/kobject.h"
 
-extern kutil::heap_allocator g_kernel_heap;
-
 // TODO: per-cpu this?
 static j6_koid_t next_koid;