[kernel] Spit out vm_area types

The vm_space allow() functionality was a bit janky; using VMAs for all
regions would be a lot cleaner. To that end, this change:

- Adds a "static array" ctor to kutil::vector for setting the kernel
  address space's VMA list. This way a kernel heap VMA can be created
  without the heap already existing.
- Splits vm_area into different subclasses depending on desired behavior
- Splits out the concept of vm_mapper which maps vm_areas to vm_spaces,
  so that some kinds of VMA can be inherently single-space
- Implements VMA resizing so that userspace can grow allocations.
- Obsolete page_table_indices is removed

Also, the following bugs were fixed:

- kutil::map iterators on empty maps no longer break
- memory::page_count was doing page-align, not page-count

See: Github bug #242
See: [frobozz blog post](https://jsix.dev/posts/frobozz/)

Tags:

src/include/syscalls.inc

@@ -24,8 +24,9 @@ SYSCALL(0x2a, endpoint_send,     j6_handle_t, size_t, void *)
 SYSCALL(0x2b, endpoint_receive,  j6_handle_t, size_t *, void *)
 SYSCALL(0x2c, endpoint_sendrecv, j6_handle_t, size_t *, void *)
 
-SYSCALL(0x30, vma_create,        j6_handle_t *, size_t)
-SYSCALL(0x31, vma_create_map,    j6_handle_t *, size_t, uintptr_t)
+SYSCALL(0x30, vma_create,        j6_handle_t *, size_t, uint32_t)
+SYSCALL(0x31, vma_create_map,    j6_handle_t *, size_t, uintptr_t, uint32_t)
 SYSCALL(0x32, vma_close,         j6_handle_t)
 SYSCALL(0x33, vma_map,           j6_handle_t, uintptr_t)
 SYSCALL(0x34, vma_unmap,         j6_handle_t)
+SYSCALL(0x34, vma_resize,        j6_handle_t, size_t *)