Tableselect rows can be disabled

It's possible now to disable tableselect rows by setting the #disabled property on the rows to be disabled.

$header = [
  'first_name' => $this->t('First Name'),
  'last_name' => $this->t('Last Name'),
];

$options = [
  1 => ['first_name' => 'Indy', 'last_name' => 'Jones'],
  2 => ['first_name' => 'Darth', 'last_name' => 'Vader'],
  // Prevent users from selecting this row by adding a '#disabled' property set
  // to TRUE.
  3 => ['first_name' => 'Super', 'last_name' => 'Man', '#disabled' => TRUE],
];

$form['table'] = array(
  '#type' => 'tableselect',
  '#header' => $header,
  '#options' => $options,
  '#empty' => $this->t('No users found'),
);