[APM] Migrate /environment to deployment agnostic test (#199582)

## Summary

Closes #198969
Part of #193245

This PR contains the changes to migrate `environment` 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.serverless.config.ts
node scripts/functional_test_runner --config x-pack/test/api_integration/deployment_agnostic/configs/serverless/oblt.serverless.config.ts --grep="APM"
```

It's recommended to be run against
[MKI](https://github.com/crespocarlos/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.stateful.config.ts
node scripts/functional_test_runner --config x-pack/test/api_integration/deployment_agnostic/configs/stateful/oblt.stateful.config.ts --grep="APM"
```

## Checks

- [ ] (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

x-pack/test/api_integration/deployment_agnostic/apis/observability/apm/environment/get_environment.spec.ts

@@ -0,0 +1,155 @@
+/*
+ * 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 { apm, timerange } from '@kbn/apm-synthtrace-client';
+import type { ApmSynthtraceEsClient } from '@kbn/apm-synthtrace';
+import type { DeploymentAgnosticFtrProviderContext } from '../../../../ftr_provider_context';
+
+async function generateData({
+  apmSynthtraceEsClient,
+  start,
+  end,
+}: {
+  apmSynthtraceEsClient: ApmSynthtraceEsClient;
+  start: number;
+  end: number;
+}) {
+  const environmentNames = ['production', 'development', 'staging'];
+  const serviceNames = ['go', 'java', 'node'];
+
+  const services = environmentNames.flatMap((environment) => {
+    return serviceNames.flatMap((serviceName) => {
+      return apm
+        .service({
+          name: serviceName,
+          environment,
+          agentName: serviceName,
+        })
+        .instance('instance-a');
+    });
+  });
+
+  const goServiceWithAdditionalEnvironment = apm
+    .service({
+      name: 'go',
+      environment: 'custom-go-environment',
+      agentName: 'go',
+    })
+    .instance('instance-a');
+
+  // Generate a transaction for each service
+  const docs = timerange(start, end)
+    .ratePerMinute(1)
+    .generator((timestamp) => {
+      const loopGeneratedDocs = services.flatMap((service) => {
+        return service
+          .transaction({ transactionName: 'GET /api/product/:id' })
+          .timestamp(timestamp)
+          .duration(1000);
+      });
+
+      const customDoc = goServiceWithAdditionalEnvironment
+        .transaction({
+          transactionName: 'GET /api/go/memory',
+          transactionType: 'custom-go-type',
+        })
+        .timestamp(timestamp)
+        .duration(1000);
+
+      return [...loopGeneratedDocs, customDoc];
+    });
+
+  return apmSynthtraceEsClient.index(docs);
+}
+
+const startNumber = new Date('2021-01-01T00:00:00.000Z').getTime();
+const endNumber = new Date('2021-01-01T00:05:00.000Z').getTime() - 1;
+
+const start = new Date(startNumber).toISOString();
+const end = new Date(endNumber).toISOString();
+
+export default function environmentsAPITests({ getService }: DeploymentAgnosticFtrProviderContext) {
+  const apmApiClient = getService('apmApi');
+  const synthtrace = getService('synthtrace');
+
+  describe('get environments', () => {
+    let apmSynthtraceEsClient: ApmSynthtraceEsClient;
+
+    before(async () => {
+      apmSynthtraceEsClient = await synthtrace.createApmSynthtraceEsClient();
+      await generateData({
+        apmSynthtraceEsClient,
+        start: startNumber,
+        end: endNumber,
+      });
+    });
+
+    after(async () => {
+      await apmSynthtraceEsClient.clean();
+    });
+
+    describe('when service name is not specified', () => {
+      it('returns all environments', async () => {
+        const { body } = await apmApiClient.readUser({
+          endpoint: 'GET /internal/apm/environments',
+          params: {
+            query: { start, end },
+          },
+        });
+
+        expect(body.environments.length).to.be.equal(4);
+        expectSnapshot(body.environments).toMatchInline(`
+            Array [
+              "development",
+              "production",
+              "staging",
+              "custom-go-environment",
+            ]
+          `);
+      });
+    });
+
+    describe('when service name is specified', () => {
+      it('returns service specific environments for go', async () => {
+        const { body } = await apmApiClient.readUser({
+          endpoint: 'GET /internal/apm/environments',
+          params: {
+            query: { start, end, serviceName: 'go' },
+          },
+        });
+
+        expect(body.environments.length).to.be.equal(4);
+        expectSnapshot(body.environments).toMatchInline(`
+            Array [
+              "custom-go-environment",
+              "development",
+              "production",
+              "staging",
+            ]
+          `);
+      });
+
+      it('returns service specific environments for java', async () => {
+        const { body } = await apmApiClient.readUser({
+          endpoint: 'GET /internal/apm/environments',
+          params: {
+            query: { start, end, serviceName: 'java' },
+          },
+        });
+
+        expect(body.environments.length).to.be.equal(3);
+        expectSnapshot(body.environments).toMatchInline(`
+            Array [
+              "development",
+              "production",
+              "staging",
+            ]
+          `);
+      });
+    });
+  });
+}

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

@@ -0,0 +1,14 @@
+/*
+ * 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 { DeploymentAgnosticFtrProviderContext } from '../../../../ftr_provider_context';
+
+export default function ({ loadTestFile }: DeploymentAgnosticFtrProviderContext) {
+  describe('environment', () => {
+    loadTestFile(require.resolve('./get_environment.spec.ts'));
+  });
+}

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

@@ -16,6 +16,7 @@ export default function apmApiIntegrationTests({
     loadTestFile(require.resolve('./mobile'));
     loadTestFile(require.resolve('./custom_dashboards'));
     loadTestFile(require.resolve('./dependencies'));
+    loadTestFile(require.resolve('./environment'));
     loadTestFile(require.resolve('./error_rate'));
     loadTestFile(require.resolve('./data_view'));
     loadTestFile(require.resolve('./correlations'));