[ML] Increase Test Coverage 8.16.0

[peteharverson]

Follow up to #182235

Meta issue to summarize improvements to test coverage for 8.16.0.

Jest unit tests

• [x] https://github.com/elastic/kibana/pull/188913 (WR)
• [x] https://github.com/elastic/kibana/pull/189155 (WR)
• [x] https://github.com/elastic/kibana/pull/189863 (WR)

API integration tests

• [x] POST /internal/file_upload/preview_tika_contents (JG) https://github.com/elastic/kibana/pull/186956
• [ ] POST /internal/ml/_has_privileges
• [ ] POST /internal/ml/anomaly_detectors/:jobId/results/buckets (RJ)
• [ ] POST /internal/ml/anomaly_detectors/:jobId/results/overall_buckets (RJ)
• [ ] POST /internal/ml/anomaly_detectors/_validate/detector
• [ ] DELETE /internal/ml/datafeeds/:datafeedId
• [ ] 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)

Serverless tests

Functional tests

• [x] Click action on anomaly markers in embeddables (MA) https://github.com/elastic/kibana/pull/187801
• [ ] Memory usage page (include check for memory usage chart) (RJ)
• [ ] SMV: Assert that it should not show a chart until the partition field is selected (DA) https://github.com/elastic/kibana/pull/189729#issuecomment-2288581171
• [ ] SMV: Assert annotations and anomalies table content. https://github.com/elastic/kibana/pull/189729#issuecomment-2288722912 (at the moment we only assert if exists)
• [ ] AD jobs list: Stop datafeed action https://github.com/elastic/kibana/pull/189729#issuecomment-2288679629

Performance testing journey

Accessibility tests

part of #88496

• [ ] Model management - Trained models list (RJ)
• [ ] Memory usage page

[elasticmachine]

Pinging @elastic/ml-ui (:ml)