Move ML tests to be sub-projects of ML (#33026)

This commit moves the ML QA tests to be a sub-project of ML. The purpose
of this refactoring is to enable ML developers to run
:x-pack:plugin:ml:check and run the vast majority of a ML tests with a
single command (this still does not contain the ML REST tests, nor the
upgrade tests). This simplifies local development for faster iteration.

x-pack/plugin/ml/build.gradle

@@ -103,9 +103,19 @@ task internalClusterTest(type: RandomizedTestingTask,
   include '**/*IT.class'
   systemProperty 'es.set.netty.runtime.available.processors', 'false'
 }
+
 check.dependsOn internalClusterTest
 internalClusterTest.mustRunAfter test
 
+// add all sub-projects of the qa sub-project
+gradle.projectsEvaluated {
+    project.subprojects
+            .find { it.path == project.path + ":qa" }
+            .subprojects
+            .findAll { it.path.startsWith(project.path + ":qa") }
+            .each { check.dependsOn it.check }
+}
+
 // also add an "alias" task to make typing on the command line easier
 task icTest {
   dependsOn internalClusterTest

x-pack/plugin/ml/qa/build.gradle

@@ -0,0 +1,31 @@
+import org.elasticsearch.gradle.test.RestIntegTestTask
+
+subprojects {
+    // HACK: please fix this
+    // we want to add the rest api specs for xpack to qa tests, but we
+    // need to wait until after the project is evaluated to only apply
+    // to those that rest tests. this used to be done automatically
+    // when xpack was a plugin, but now there is no place with xpack as a module.
+    // instead, we should package these and make them easy to use for rest tests,
+    // but currently, they must be copied into the resources of the test runner.
+    project.tasks.withType(RestIntegTestTask) {
+        File xpackResources = new File(xpackProject('plugin').projectDir, 'src/test/resources')
+        project.copyRestSpec.from(xpackResources) {
+            include 'rest-api-spec/api/**'
+        }
+    }
+}
+
+gradle.projectsEvaluated {
+    subprojects {
+        Task assemble = project.tasks.findByName('assemble')
+        if (assemble) {
+            project.tasks.remove(assemble)
+            project.build.dependsOn.remove('assemble')
+        }
+        Task dependenciesInfo = project.tasks.findByName('dependenciesInfo')
+        if (dependenciesInfo) {
+            project.precommit.dependsOn.remove('dependenciesInfo')
+        }
+    }
+}