title: Flutter - Change search hint text of SearchDelegate
body: <p>In current implementation of <code>SearchDelegate</code>, there is no option to change the hint text. When the query is empty, search screen is displaying <strong>"Search"</strong> in the query field as a hint text. </p>
  
  <p>Hint text is currently defined on line 395 as follows:</p>
  
  <pre><code>final String searchFieldLabel = MaterialLocalizations.of(context).searchFieldLabel;
  </code></pre>
  
  <p>There is, however, an <a href="https://github.com/flutter/flutter/issues/18831" rel="noreferrer">existing issue to this subject reported</a>.</p>
  
  <p>I wasn't able to come up with any solution for this.
  Do you know any workaround for the issue?</p>