Move async search yaml tests to x-pack yaml test folder (elastic#53537)

The yaml tests for async search currently sit in its qa folder. There is no reason though for them to live in a separate folder as they don't require particular setup. This commit moves them to the main folder together with the other x-pack yaml tests so that they will be run by the client test runners too.

x-pack/plugin/async-search/qa/security/src/test/java/org/elasticsearch/xpack/search/AsyncSearchSecurityIT.java

@@ -19,6 +19,7 @@
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.common.xcontent.json.JsonXContent;
+import org.elasticsearch.test.rest.ESRestTestCase;
 import org.junit.Before;
 
 import java.io.IOException;
@@ -31,7 +32,7 @@
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
 
-public class AsyncSearchSecurityIT extends AsyncSearchRestTestCase {
+public class AsyncSearchSecurityIT extends ESRestTestCase {
     /**
      * All tests run as a superuser but use <code>es-security-runas-user</code> to become a less privileged user.
      */