[Response Ops][Task Manager] Integration test for switching between t…

…ask claim strategies (elastic#186419)

Resolves elastic#184941

## Summary

Adds integration test to verify that restarting Kibana with a different
task claim strategy does not break anything and tasks are claimed as
expected.

---------

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>

x-pack/plugins/task_manager/server/integration_tests/lib/setup_test_servers.ts

@@ -8,19 +8,8 @@
 import deepmerge from 'deepmerge';
 import { createTestServers, createRootWithCorePlugins } from '@kbn/core-test-helpers-kbn-server';
 
-export async function setupTestServers(settings = {}) {
-  const { startES } = createTestServers({
-    adjustTimeout: (t) => jest.setTimeout(t),
-    settings: {
-      es: {
-        license: 'trial',
-      },
-    },
-  });
-
-  const esServer = await startES();
-
-  const root = createRootWithCorePlugins(
+function createRoot(settings = {}) {
+  return createRootWithCorePlugins(
     deepmerge(
       {
         logging: {
@@ -32,13 +21,35 @@ export async function setupTestServers(settings = {}) {
               name: 'plugins.taskManager',
               level: 'all',
             },
+            {
+              name: 'plugins.taskManager.metrics-debugger',
+              level: 'warn',
+            },
+            {
+              name: 'plugins.taskManager.metrics-subscribe-debugger',
+              level: 'warn',
+            },
           ],
         },
       },
       settings
     ),
     { oss: false }
   );
+}
+export async function setupTestServers(settings = {}) {
+  const { startES } = createTestServers({
+    adjustTimeout: (t) => jest.setTimeout(t),
+    settings: {
+      es: {
+        license: 'trial',
+      },
+    },
+  });
+
+  const esServer = await startES();
+
+  const root = createRoot(settings);
 
   await root.preboot();
   const coreSetup = await root.setup();
@@ -54,3 +65,20 @@ export async function setupTestServers(settings = {}) {
     },
   };
 }
+
+export async function setupKibanaServer(settings = {}) {
+  const root = createRoot(settings);
+
+  await root.preboot();
+  const coreSetup = await root.setup();
+  const coreStart = await root.start();
+
+  return {
+    kibanaServer: {
+      root,
+      coreSetup,
+      coreStart,
+      stop: async () => await root.shutdown(),
+    },
+  };
+}