[ML] Increase Test Coverage 8.18.0

[peteharverson]

Follow up to #197420

Meta issue to summarize improvements to test coverage for 8.18.0.

Jest unit tests

• [ML] Trained Models: Optimize trained models Kibana API #200977 (DA)
• [ML] Anomaly Explorer: Enhancements for Embeddables with Selected Groups & Explorer Refactor #203224 (RJ)
• Trained models NER test [ML] Borealis theme fixes (tokens) #203518 (WR)

API integration tests

• DELETE /internal/ml/datafeeds/:datafeedId
• GET /internal/ml/trained_models_list (DA) [ML] Trained Models: Optimize trained models Kibana API #200977
• GET /internal/ml/trained_models/ingest_pipelines (DA) (look to remove this endpoint)
• POST /internal/ml/trained_models/create_inference_pipeline (DA) (look to remove this endpoint)
• Move some AIOps API tests to the deployment agnostic (serverless and stateful) folder

Serverless tests

• Management -> Machine Learning page. For all project types.
• Memory Usage. Check ML entities are filtered according to the project type.
• Notifications page. Check ML entities are filtered according to the project type.

Functional tests

• Attaching a log rate analysis embeddable to a case (RJ) [ML] Adds action to add log rate analysis to a case #201549
• SMV: Assert that it should not show a chart until the partition field is selected (DA) [ML] Remove dependency cache. #189729 (comment)
• SMV: Assert annotations and anomalies table content. [ML] Remove dependency cache. #189729 (comment) (at the moment we only assert if exists)
• AD jobs list: Stop datafeed action [ML] Remove dependency cache. #189729 (comment)

Performance testing journeys

Accessibility tests

part of #88496

• Stack Management Anomaly detection jobs list
• Data frame analytics jobs list
• Trained models list

[elasticmachine]

Pinging @elastic/ml-ui (:ml)