[ci] Run serverless test suites on merge (#158685)

After a pull request has been merged, the `kibana-on-merge` pipeline
will
trigger a new pipeline, `kibana-serverless`.  This pipeline contains our
serverless tests and will initially be non-blocking.

These tests will be merged into `kibana-on-merge` when proven stable.

https://buildkite.com/elastic/kibana-serverless

.buildkite/pipelines/on_merge.yml

@@ -86,6 +86,14 @@ steps:
     agents:
       queue: 'kibana-default'
 
+  - command: '.buildkite/scripts/steps/functional/on_merge_serverless_ftrs.sh'
+    label: Trigger serverless ftr tests
+    timeout_in_minutes: 10
+    depends_on:
+      - build
+    agents:
+      queue: 'kibana-default'
+
   - command: .buildkite/scripts/steps/lint.sh
     label: 'Linting'
     agents:

.buildkite/pipelines/serverless.yml

@@ -0,0 +1,74 @@
+steps:
+  - command: .buildkite/scripts/lifecycle/pre_build.sh
+    label: Pre-Build
+    timeout_in_minutes: 10
+    agents:
+      queue: kibana-default
+    retry:
+      automatic:
+        - exit_status: '*'
+          limit: 1
+
+  - command: .buildkite/scripts/steps/build_kibana.sh
+    label: Build Kibana Distribution and Plugins
+    agents:
+      queue: n2-16-spot
+    key: build
+    if: "build.env('KIBANA_BUILD_ID') == null || build.env('KIBANA_BUILD_ID') == ''"
+    timeout_in_minutes: 60
+    retry:
+      automatic:
+        - exit_status: '-1'
+          limit: 3
+
+  - command: SERVERLESS_ENVIRONMENT=common .buildkite/scripts/steps/functional/serverless_ftr.sh
+    label: 'Serverless Common Tests'
+    agents:
+      queue: n2-4-spot
+    depends_on: build
+    timeout_in_minutes: 40
+    retry:
+      automatic:
+        - exit_status: '-1'
+          limit: 3
+        - exit_status: '*'
+          limit: 1
+
+  - command: SERVERLESS_ENVIRONMENT=observability .buildkite/scripts/steps/functional/serverless_ftr.sh
+    label: 'Serverless Observability Tests'
+    agents:
+      queue: n2-4-spot
+    depends_on: build
+    timeout_in_minutes: 40
+    retry:
+      automatic:
+        - exit_status: '-1'
+          limit: 3
+        - exit_status: '*'
+          limit: 1
+
+  - command: SERVERLESS_ENVIRONMENT=search .buildkite/scripts/steps/functional/serverless_ftr.sh
+    label: 'Serverless Search Tests'
+    agents:
+      queue: n2-4-spot
+    depends_on: build
+    timeout_in_minutes: 40
+    retry:
+      automatic:
+        - exit_status: '-1'
+          limit: 3
+        - exit_status: '*'
+          limit: 1
+
+  - command: SERVERLESS_ENVIRONMENT=security .buildkite/scripts/steps/functional/serverless_ftr.sh
+    label: 'Serverless Security Tests'
+    agents:
+      queue: n2-4-spot
+    depends_on: build
+    timeout_in_minutes: 40
+    retry:
+      automatic:
+        - exit_status: '-1'
+          limit: 3
+        - exit_status: '*'
+          limit: 1

.buildkite/scripts/steps/functional/on_merge_serverless_ftrs.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+
+set -euo pipefail
+
+if [[ "$BUILDKITE_BRANCH" == "main" ]]; then
+  echo "--- Trigger serverless ftr tests"
+  ts-node .buildkite/scripts/steps/trigger_pipeline.ts kibana-serverless "$BUILDKITE_BRANCH" "$BUILDKITE_COMMIT" "$BUILDKITE_BUILD_ID"
+fi

x-pack/test_serverless/shared/config.base.ts

@@ -9,7 +9,6 @@ import { resolve } from 'path';
 import { format as formatUrl } from 'url';
 
 import { REPO_ROOT } from '@kbn/repo-info';
-
 import { esTestConfig, kbnTestConfig, kibanaServerTestUser } from '@kbn/test';
 
 export default async () => {