[APM] create synthtrace scenario with ML anomalies (#194125)

This PR only adds a new synthtrace scenario that generated ML anomalies.

```
node scripts/synthtrace.js apm_ml_anomalies --from=2024-09-01T08:00:00.000Z --to=2024-09-08T08:00:00.000Z
```

packages/kbn-apm-synthtrace/src/scenarios/apm_ml_anomalies.ts

@@ -0,0 +1,61 @@
+/*
+ * 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", the "GNU Affero General Public License v3.0 only", 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", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+import { apm, ApmFields } from '@kbn/apm-synthtrace-client';
+import { range as _range } from 'lodash';
+import { Scenario } from '../cli/scenario';
+import { withClient } from '../lib/utils/with_client';
+
+const spikeStart = new Date('2024-09-03T00:00:00.000Z').getTime();
+const spikeEnd = new Date('2024-09-03T02:00:00.000Z').getTime();
+const NORMAL_DURATION = 100;
+const NORMAL_RATE = 1;
+
+const scenario: Scenario<ApmFields> = async (runOptions) => {
+  const { logger } = runOptions;
+
+  return {
+    generate: ({ range, clients: { apmEsClient } }) => {
+      const serviceA = apm.service('a', 'production', 'java').instance('a');
+      const serviceB = apm.service('b', 'production', 'go').instance('b');
+
+      const apmData = range
+        .interval('1m')
+        .rate(1)
+        .generator((timestamp) => {
+          const isInSpike = timestamp >= spikeStart && timestamp < spikeEnd;
+          const count = isInSpike ? 4 : NORMAL_RATE;
+          const duration = isInSpike ? 1000 : NORMAL_DURATION;
+          const outcome = isInSpike ? 'failure' : 'success';
+          return [
+            ..._range(0, count).flatMap((_) =>
+              serviceA
+                .transaction('tx', 'request')
+                .timestamp(timestamp)
+                .duration(duration)
+                .outcome(outcome)
+            ),
+            serviceB.transaction('tx', 'Worker').timestamp(timestamp).duration(duration).success(),
+            serviceB
+              .transaction('tx2', 'request')
+              .timestamp(timestamp)
+              .duration(NORMAL_DURATION)
+              .success(),
+          ];
+        });
+
+      return withClient(
+        apmEsClient,
+        logger.perf('generating_apm_events', () => apmData)
+      );
+    },
+  };
+};
+
+export default scenario;