kernel: heap: Add allocation metadata to allocated_bytes

The allocated_bytes were missing the allocation metadata. Because of that
the sum of free_bytes and allocated_bytes doesn't remain constant after
each allocation. This convention doesn't match glibc's behavior. This
commit changes the chunksz_to_bytes function to include the metadata in the
calculation. The analysis of the mallinfo2 function from glibc has been
done in #92392 Pull Request.

Signed-off-by: Krzysztof Sychla <ksychla@antmicro.com>

lib/heap/heap.h

@@ -255,7 +255,7 @@ static inline chunksz_t min_chunk_size(struct z_heap *h)
 
 static inline size_t chunksz_to_bytes(struct z_heap *h, chunksz_t chunksz_in)
 {
-	return chunksz_in * CHUNK_UNIT - chunk_header_bytes(h);
+	return chunksz_in * CHUNK_UNIT;
 }
 
 static inline int bucket_idx(struct z_heap *h, chunksz_t sz)

samples/basic/sys_heap/sample.yaml

@@ -9,8 +9,8 @@ common:
     type: multi_line
     ordered: true
     regex:
-      - ".*allocated 15.,.*"
-      - ".*allocated 10.,.*"
+      - ".*allocated 16.,.*"
+      - ".*allocated 1..,.*"
       - ".*allocated 0, free ..., max allocated ..., heap size 256.*"
 tests:
   sample.basic.sys_heap: