[kernel] Move more from kutil to kernel

The moving of kernel-only code out of kutil continues. (See 042f061)
This commit moves the following:

- The heap allocator code
- memory.cpp/h which means:
  - letting string.h be the right header for memset and memcpy, still
    including an implementation of it for the kernel though, since
    we're not linking libc to the kernel
  - Changing calls to kalloc/kfree to new/delete in kutil containers
    that aren't going to be merged into the kernel
- Fixing a problem with stdalign.h from libc, which was causing issues
  for type_traits.

src/kernel/objects/channel.cpp

@@ -1,3 +1,4 @@
+#include <string.h>
 #include "kutil/assert.h"
 
 #include "kernel_memory.h"
@@ -38,7 +39,7 @@ channel::enqueue(size_t *len, const void *data)
     size_t avail = m_buffer.reserve(*len, &buffer);
     *len = *len > avail ? avail : *len;
 
-    kutil::memcpy(buffer, data, *len);
+    memcpy(buffer, data, *len);
     m_buffer.commit(*len);
 
     assert_signal(j6_signal_channel_can_recv);
@@ -65,7 +66,7 @@ channel::dequeue(size_t *len, void *data)
     size_t avail = m_buffer.get_block(&buffer);
     *len = *len > avail ? avail : *len;
 
-    kutil::memcpy(data, buffer, *len);
+    memcpy(data, buffer, *len);
     m_buffer.consume(*len);
 
     assert_signal(j6_signal_channel_can_send);