Overhaul memory allocation model

This commit makes several fundamental changes to memory handling:

- the frame allocator is now only an allocator for free frames, and does
  not track used frames.
- the frame allocator now stores its free list inside the free frames
  themselves, as a hybrid stack/span model.
  - This has the implication that all frames must currently fit within
    the offset area.
- kutil has a new allocator interface, which is the only allowed way for
  any code outside of src/kernel to allocate. Code under src/kernel
  _may_ use new/delete, but should prefer the allocator interface.
- the heap manager has become heap_allocator, which is merely an
  implementation of kutil::allocator which doles out sections of a given
  address range.
- the heap manager now only writes block headers when necessary,
  avoiding page faults until they're actually needed
- page_manager now has a page fault handler, which checks with the
  address_manager to see if the address is known, and provides a frame
  mapping if it is, allowing heap manager to work with its entire
  address size from the start. (Currently 32GiB.)

src/tests/main.cpp

@@ -1,46 +1,2 @@
 #define CATCH_CONFIG_MAIN
 #include "catch.hpp"
-
-#include <malloc.h>
-void * operator new (size_t n)					{ return ::malloc(n); }
-void * operator new[] (size_t n)				{ return ::malloc(n); }
-void operator delete (void *p) noexcept			{ return ::free(p); }
-void operator delete[] (void *p) noexcept		{ return ::free(p); }
-
-#include "kutil/heap_manager.h"
-#include "kutil/memory.h"
-
-struct default_heap_listener : 
-	public Catch::TestEventListenerBase
-{
-	using TestEventListenerBase::TestEventListenerBase;
-
-	virtual void testCaseStarting(Catch::TestCaseInfo const& info) override
-	{
-		heap = new kutil::heap_manager(heap_grow_callback);
-		kutil::setup::set_heap(heap);
-	}
-
-	virtual void testCaseEnded(Catch::TestCaseStats const& stats) override
-	{
-		kutil::setup::set_heap(nullptr);
-		delete heap;
-
-		for (void *p : memory) ::free(p);
-		memory.clear();
-	}
-
-	static std::vector<void *> memory;
-	static kutil::heap_manager *heap;
-
-	static void * heap_grow_callback(size_t length) {
-		void *p = aligned_alloc(length, length);
-		memory.push_back(p);
-		return p;
-	}
-};
-
-std::vector<void *> default_heap_listener::memory;
-kutil::heap_manager *default_heap_listener::heap;
-
-CATCH_REGISTER_LISTENER( default_heap_listener );