NameFormatterService: Harden

Problem/Motivation

The url is currently created by concating strings.

    if (!empty($components['url'])) {
      $name = new FormattableMarkup('<a href=":link">' . $name . '</a>', [
        ':link' => $components['url']->toString(),
      ]);
    }

Steps to reproduce

Proposed resolution

$name = $this->parser->parse($components, $format_string, $this->settings);
$safe_name = $name instanceof MarkupInterface ? $name : Html::escape((string) $name);
if (!empty($components['url'])) {
  $name = new FormattableMarkup('<a href=":link">@name</a>', [
    ':link' => $components['url']->toString(),
    '@name' => $safe_name,
  ]);
}

Remaining tasks

Add a regression test that pushes <script>alert(1)</script> through NameFormatter::viewElements() and asserts it's sanitized.

User interface changes

API changes

Data model changes