[kernel] Change heap alloc for better alignment

Created a new util/node_map.h that implements a map that grows in-place.
Now this is used for tracking blocks' size orders, instead of a header
at the start of the memory block. This allows the whole buddy block to
be allocated, allowing for page-aligned (or greater) blocks to be
requested from the heap.

definitions/memory_layout.yaml

@@ -7,8 +7,11 @@
   size: 1T
   shared: true
 
+- name: heapmap
+  size: 32G
+
 - name: heap
-  size: 64G
+  size: 32G
 
 - name: stacks
   size: 64G