Configure TREL feature from feature flag.

Bug: 354868035
Bug: 359089751

Test: atest ThreadNetworkIntegrationTests:ServiceDiscoveryTest#trel_servicePublished

Change-Id: Ib545df6bf5ce20f35914b4695dbd2e3c1e1232e4
diff --git a/thread/tests/integration/AndroidTest.xml b/thread/tests/integration/AndroidTest.xml
index 8f98941..08409b4 100644
--- a/thread/tests/integration/AndroidTest.xml
+++ b/thread/tests/integration/AndroidTest.xml
@@ -48,4 +48,10 @@
     <test class="com.android.tradefed.testtype.AndroidJUnitTest" >
         <option name="package" value="com.android.thread.tests.integration" />
     </test>
+
+    <!-- Enable TREL for integration tests -->
+    <target_preparer class="com.android.tradefed.targetprep.FeatureFlagTargetPreparer">
+        <option name="flag-value"
+                value="thread_network/TrelFeature__enabled=true"/>
+    </target_preparer>
 </configuration>