[CI] automatically commit SO def change snapshot (elastic#169610)

Fix elastic#147935

Automatically run the SO def integration test, and commit the changes if
any, as a new CI check script.

As explained in the issue, this is just some DX improvement, avoiding
for the developer the inconvenience of doing it manually every time they
change or add a SO in any PR.

.buildkite/scripts/steps/checks.sh

@@ -22,5 +22,6 @@ export DISABLE_BOOTSTRAP_VALIDATION=false
 .buildkite/scripts/steps/checks/test_hardening.sh
 .buildkite/scripts/steps/checks/ftr_configs.sh
 .buildkite/scripts/steps/checks/saved_objects_compat_changes.sh
+.buildkite/scripts/steps/checks/saved_objects_definition_change.sh
 .buildkite/scripts/steps/code_generation/security_solution_codegen.sh
 .buildkite/scripts/steps/checks/yarn_deduplicate.sh

.buildkite/scripts/steps/checks/saved_objects_definition_change.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+source .buildkite/scripts/common/util.sh
+
+echo --- Check SO definition changes
+cmd="node scripts/jest_integration -u src/core/server/integration_tests/ci_checks"
+
+eval "$cmd"
+check_for_changed_files "$cmd" true

src/core/server/integration_tests/ci_checks/jest.integration.config.js

@@ -0,0 +1,20 @@
+/*
+ * 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 = {
+  bail: true, // only report 1 issue
+  // 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/ci_checks'],
+  // must override to match all test given there is no `integration_tests` subfolder
+  testMatch: ['**/*.test.{js,mjs,ts,tsx}'],
+};