[zion] Add a basic slab allocator to the kernel.

Don't free from the slab allocator yet but allocations appear to work.

zion/memory/kernel_heap.h

@@ -1,19 +1,31 @@
 #pragma once
 
+#include <glacier/memory/unique_ptr.h>
 #include <stdint.h>
 
+#include "memory/slab_allocator.h"
+
 class KernelHeap {
  public:
   KernelHeap(uint64_t lower_bound, uint64_t upper_bound);
+  void InitializeSlabAllocators();
 
   void* Allocate(uint64_t size);
 
+  void Free(void* address);
+
   static void DumpDistribution();
 
  private:
+  uint64_t next_slab_addr_;
+  uint64_t first_unsized_addr_;
   uint64_t next_addr_;
   uint64_t upper_bound_;
 
+  glcr::UniquePtr<SlabAllocator<8>> slab_8_;
+  glcr::UniquePtr<SlabAllocator<16>> slab_16_;
+  glcr::UniquePtr<SlabAllocator<32>> slab_32_;
+
   // Distribution collection for the purpose of investigating a slab allocator.
   // 0: 0-4B
   // 1: 4B-8B