[APM] Migrate /transactions to deployment agnostic test (elastic#20…

…0694)

## Summary

Closes elastic#198997
Part of elastic#193245

This PR contains the changes to migrate `transactions` test folder to
Deployment-agnostic testing strategy.

### How to test

- Serverless

```
node scripts/functional_tests_server --config x-pack/test/api_integration/deployment_agnostic/configs/serverless/oblt.apm.serverless.config.ts
node scripts/functional_test_runner --config x-pack/test/api_integration/deployment_agnostic/configs/serverless/oblt.apm.serverless.config.ts
```

It's recommended to be run against
[MKI](https://github.com/elastic/kibana/blob/main/x-pack/test_serverless/README.md#run-tests-on-mki)

- Stateful
```
node scripts/functional_tests_server --config x-pack/test/api_integration/deployment_agnostic/configs/stateful/oblt.apm.stateful.config.ts
node scripts/functional_test_runner --config x-pack/test/api_integration/deployment_agnostic/configs/stateful/oblt.apm.stateful.config.ts
```

## Checks

- [x] (OPTIONAL, only if a test has been unskipped) Run flaky test suite
- [x] local run for serverless
- [x] local run for stateful
- [x] MKI run for serverless 

<!--ONMERGE {"backportTargets":["8.x"]} ONMERGE-->

x-pack/test/api_integration/deployment_agnostic/apis/observability/apm/index.ts

@@ -38,6 +38,7 @@ export default function apmApiIntegrationTests({
     loadTestFile(require.resolve('./span_links'));
     loadTestFile(require.resolve('./suggestions'));
     loadTestFile(require.resolve('./throughput'));
+    loadTestFile(require.resolve('./transactions'));
     loadTestFile(require.resolve('./service_overview'));
   });
 }

x-pack/test/api_integration/deployment_agnostic/apis/observability/apm/transactions/breakdown.spec.ts

@@ -0,0 +1,41 @@
+/*
+ * 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; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import expect from '@kbn/expect';
+import archives from '../constants/archives_metadata';
+import type { DeploymentAgnosticFtrProviderContext } from '../../../../ftr_provider_context';
+
+export default function ApiTest({ getService }: DeploymentAgnosticFtrProviderContext) {
+  const apmApiClient = getService('apmApi');
+
+  const archiveName = 'apm_8.0.0';
+  const { start, end } = archives[archiveName];
+  const transactionType = 'request';
+
+  describe('Breakdown', () => {
+    describe('when data is not loaded', () => {
+      it('handles the empty state', async () => {
+        const response = await apmApiClient.readUser({
+          endpoint: 'GET /internal/apm/services/{serviceName}/transaction/charts/breakdown',
+          params: {
+            path: { serviceName: 'opbeans-node' },
+            query: {
+              start,
+              end,
+              transactionType,
+              environment: 'ENVIRONMENT_ALL',
+              kuery: '',
+            },
+          },
+        });
+
+        expect(response.status).to.be(200);
+        expect(response.body).to.eql({ timeseries: [] });
+      });
+    });
+  });
+}