Fix content security policy failure due to <script> tags without nonce generated by HtmlDumper

[Yannik]

Short Version:
This PR fixes csp errors caused by <script> tags without a nonce generated by HtmlDumper.

Long version:

JavaScriptRenderer::render() adds content using JavaScriptRenderer::getAddDatasetCode() with data from JavaScriptRenderer::getData(), which returns data from JavaScriptRenderer::collect().

JavaScriptRenderer::collect() essentially does this:

foreach ($this->collectors as $name => $collector) {
    $this->data[$name] = $collector->collect();
}

For the both the request collector from maximebf/debugbar (default_request) and laravel-debugbar, the collect() function uses $data[$key] = $this->getVarDumper()->renderVar($GLOBALS[$var]); to render the variables.

getVarDumper() by default returns a DebugBarVarDumper instance. DebugBarVarDumper->renderVar() returns the result from DebugBarVarDumper->dump(), which, finally returns the result from Symfony\Component\VarDumper\Dumper\HtmlDumper::dump, which calls parent::dump (AbstractDumper::dump), which calls dumpLine, which embeds the data within $this->dumpSuffix, which contains:

protected $dumpSuffix = '</pre><script>Sfdump(%s)</script>';

...a <script> tag without a nonce!