Add module metadata to `ComposHostTestCases` for Mainline Presubmits.

This information is required to run `ComposHostTestCases`,
declared in the `mainline-presubmit` test group of ART's
`TEST_MAPPING` file, with Atest.

Test: atest --test-mapping art:mainline-presubmit
Bug: 258065512
Bug: 178703264
Change-Id: Idd136acf68b4b66c4a3f5db4cc3e54da2e0e82e8
diff --git a/compos/tests/AndroidTest.xml b/compos/tests/AndroidTest.xml
index 2a84291..f9e6837 100644
--- a/compos/tests/AndroidTest.xml
+++ b/compos/tests/AndroidTest.xml
@@ -14,6 +14,8 @@
      limitations under the License.
 -->
 <configuration description="Tests for CompOS">
+    <option name="config-descriptor:metadata" key="mainline-param" value="com.google.android.art.apex" />
+
     <target_preparer class="com.android.tradefed.targetprep.RootTargetPreparer">
         <option name="force-root" value="true" />
     </target_preparer>