[AI Assistant] Migrate API integration tests to the deployment agnostic solution

[maryam-saeidi]

🍒 Summary

We need to migrate API integration tests to the deployment-agnostic solution to ensure they can be run on the serverless environment and avoid duplication.
https://github.com/elastic/kibana/blob/main/x-pack/test/api_integration/deployment_agnostic/README.md

Important

Please make sure to run these tests on MKI before merging the related PR. (More info)

Existing tests

Test	ESS	Serverless	Notes
API	✅	❌	Serverless: x-pack/test_serverless/api_integration/file_path ESS: x-pack/test/api_integration/file_path

[elasticmachine]

Pinging @elastic/obs-knowledge-team (Team:obs-knowledge)

[elasticmachine]

Pinging @elastic/obs-ai-assistant (Team:Obs AI Assistant)

[emma-raffenne]

Will be addressed in #192718

[maryam-saeidi]

Hi @emma-raffenne ,
Do you have any estimates for when this work will be picked up?

[maryam-saeidi]

@emma-raffenne Since #192718 is closed, can we close this as well?

[emma-raffenne]

@maryam-saeidi yes, it's done.