[Security Solution] Extend Flaky runner 's config to run Serverless C…

…ypress tests (elastic#166783)

## Summary

This PR extends Flaky test runner's config to be able to run Serverless Cypress tests.

[Serverless Security Solution Flaky test run](https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/3189)

.buildkite/pipelines/flaky_tests/groups.json

@@ -1,21 +1,37 @@
 {
   "groups": [
+    {
+      "key": "cypress/security_solution",
+      "name": "Security Solution - Cypress"
+    },
+    {
+      "key": "cypress/security_serverless",
+      "name": "[Serverless] Security Solution - Cypress"
+    },
     {
       "key": "cypress/security_solution_investigations",
       "name": "Security Solution Investigations - Cypress"
     },
     {
-      "key": "cypress/security_solution",
-      "name": "Security Solution - Cypress"
+      "key": "cypress/security_serverless_investigations",
+      "name": "[Serverless] Security Solution Investigations - Cypress"
     },
     {
       "key": "cypress/security_solution_explore",
       "name": "Security Solution Explore - Cypress"
     },
+    {
+      "key": "cypress/security_serverless_explore",
+      "name": "[Serverless] Security Solution Explore - Cypress"
+    },
     {
       "key": "cypress/osquery_cypress",
       "name": "Osquery - Cypress"
     },
+    {
+      "key": "cypress/security_serverless_osquery",
+      "name": "[Serverless] Osquery - Cypress"
+    },
     {
       "key": "cypress/fleet_cypress",
       "name": "Fleet - Cypress"