Update auto-gen test config template with EXTRA_CONFIGS placeholder

Bug: 134509111
Test: add "require_root: true" to init_benchmarks and libpower_test
build the modules, confirm the extra target preparer is added in the
test config.

Change-Id: I2fdae79d45fd1e5866ee94d1f0e59df106be2a87

core/java_host_test_config_template.xml

@@ -17,6 +17,9 @@
 <configuration description="Runs {MODULE}">
     <option name="test-suite-tag" value="apct" />
     <option name="test-suite-tag" value="apct-junit" />
+
+    {EXTRA_CONFIGS}
+
     <test class="com.android.tradefed.testtype.HostTest" >
         <option name="jar" value="{MODULE}.jar" />
     </test>