[ftr] re-group configs for deployment agnostic tests

[dmlemeshko]

Summary

While reviewing #187924 I realised that Solution Teams will have their own stateful FTR configs and the overall number of configs in api_integration/deployment_agnostic folder might grow up soon and it is better to re-organise it in advance.

With new structure we have configs folder with 2 sub-folders: stateful and serverless

When Platform teams add deployment-agnostic tests, it is expected to be loaded in configs/stateful/platform.index.ts and at least one of <project>.serverless.config under configs/serverless

When Solution team adds deployment-agnostic tests (e.g. one of Oblt teams), it is expected to be loaded both in configs/stateful/oblt.index.ts and configs/serverless/oblt.index.ts

[dmlemeshko]

/ci

[dmlemeshko]

/ci

[kibana-ci]

💛 Build succeeded, but was flaky

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• Commit: 4d8e501

Failed CI Steps

Metrics [docs]

✅ unchanged

History

• 💔 Build #228299 failed 9cb5489
• 💛 Build #228146 was flaky 9cb5489
• 💔 Build #228137 failed 6a4677f

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@elasticmachine merge upstream

[pheyos]

LGTM