[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/drivers/nulldrv/main.cpp

@@ -63,13 +63,23 @@ main(int argc, const char **argv)
 
 	uintptr_t base = 0xcc0000000;
 	j6_handle_t vma = j6_handle_invalid;
-	j6_status_t result = _syscall_vma_create_map(&vma, 0x100000, base);
+	j6_status_t result = _syscall_vma_create_map(&vma, 0x100000, base, 1);
 	if (result != j6_status_ok)
 		return result;
 
+	size_t size = 0x800000;
+	result = _syscall_vma_resize(vma, &size);
+	if (result != j6_status_ok)
+		return result;
+
+	if (size == 0x800000)
+		_syscall_system_log("main thread resized memory area");
+
 	uint64_t *vma_ptr = reinterpret_cast<uint64_t*>(base);
-	for (int i = 0; i < 4096; ++i)
-		vma_ptr[i] = uint64_t(i);
+	for (int i = 0; i < 300; ++i)
+		vma_ptr[i * 512] = uint64_t(i);
+
+	_syscall_system_log("main thread wrote to memory area");
 
 	result = _syscall_endpoint_create(&endp);
 	if (result != j6_status_ok)
@@ -84,7 +94,7 @@ main(int argc, const char **argv)
 	_syscall_system_log("main thread created sub thread");
 
 	char message[] = "MAIN THREAD SUCCESSFULLY CALLED SENDRECV IF THIS IS LOWERCASE";
-	size_t size = sizeof(message);
+	size = sizeof(message);
 	result = _syscall_endpoint_sendrecv(endp, &size, (void*)message);
 	if (result != j6_status_ok)
 		return result;