Summary

This PR introduces grouped common configs in serverless project FTR tests.

Details

• With increasing number of added tests, we're running into issues with test run time (configurations are stopped at 40 minutes)
• This PR moves the inclusion of common tests from the projects' main config.ts file to common_configs/config.group1.ts, which can easily be extended
• As part of that, common tests in api_integration/test_suites and functional/test_suites are re-organized to no longer contain a top level index file
  • Created sub-directories and index files where needed
  • This makes it easier to group common tests when including them in project config files

Additional changes

• Add README files to x-pack/test_serverless/[api_integration|functional]/test_suites/common
• Rename security directory in common tests to platform_security to avoid confusion with the security project type
• Include sample data test suite in an index file (this suite wasn't included so far and didn't run at all) and prepared it for actually working in serverless
  • it's still failing and should be fixed soon - skipped it for now