Move some IT to a separate group (#161535)

The goal is to prevent the following warning and reduce overall CI
times:

```
The following "Jest Integration Tests" config has a duration that exceeds the maximum amount of time desired for a single CI job. This is not an error, and if you don't own this config then you can ignore this warning. If you own this config please split it up ASAP and ask Operations if you have questions about how to do that.

src/core/server/integration_tests/saved_objects/migrations/group3/jest.integration.config.js: 40.7 minutes
```

Source https://buildkite.com/elastic/kibana-pull-request/builds/140963

src/core/server/integration_tests/saved_objects/migrations/group5/jest.integration.config.js

@@ -0,0 +1,19 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+module.exports = {
+  // TODO replace the line below with
+  // preset: '@kbn/test/jest_integration_node
+  // to do so, we must fix all integration tests first
+  // see https://github.com/elastic/kibana/pull/130255/
+  preset: '@kbn/test/jest_integration',
+  rootDir: '../../../../../../..',
+  roots: ['<rootDir>/src/core/server/integration_tests/saved_objects/migrations/group5'],
+  // must override to match all test given there is no `integration_tests` subfolder
+  testMatch: ['**/*.test.{js,mjs,ts,tsx}'],
+};