Rankeval: Fold template test project into main module (#31203)

This change moves tests in `smoke-test-rank-eval-with-mustache` into the main
ranking evaluation module by declaring that the integration testing cluster
requires the `lang-mustache` plugin. This avoids having to maintain the qa
project for only one basic test suite.

Author: Christoph Büscher

modules/rank-eval/build.gradle

@@ -23,3 +23,12 @@ esplugin {
   hasClientJar = true
 }
 
+integTestCluster {
+  // Modules who's integration is explicitly tested in integration tests
+  module project(':modules:lang-mustache')
+}
+
+run {
+  // Modules who's integration is explicitly tested in integration tests
+  module project(':modules:lang-mustache')
+}