hook_layout_presave() now takes $layout object instead of $data array

Prior to Backdrop 1.7.0, hook_layout_presave() was passed a parameter named $data that was an array. After 1.7.0, this parameter is now a Layout object.

Before:

<?php
function mymodule_layout_presave($layout_name, array &$data) {
  if ($data['name'] === 'layout_name') {
    // Do something.
  }
}
?>

After:

<?php
function mymodule_layout_presave(Layout $layout) {
  if ($layout->name === 'layout_name') {
    // Do something.
  }
}
?>

It's also worth noting the documentation for hook_layout_presave() has been incorrect from the time it was introduced. It has always indicated that a $layout object was passed, but this was not the case until version 1.7.0.