[ML] Fix Trained Model stats and pipelines tab

[darnautov]

Summary

Part of #117501

• Fixes the Stats tab content
• Fixes the Pipelines tab for ML viewer
• Adds functional tests for Trained Models rows expansion

Checklist

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

Pinging @elastic/ml-ui (:ml)

[peteharverson]

Would be great to add extra checks for the actual contents of the tabs in the expanded row, but this LGTM as a first step.

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: fddd690
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• Webpack Bundle Analyzer

Test Failures

• [job] [logs] Default CI Group #15 / machine learning model management trained models for ML user with read-only access renders expanded row content correctly for model with pipelines

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
ml	3.5MB	3.5MB	+1.1KB

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @darnautov

[kibanamachine]

💚 All backports created successfully

Status	Branch	Result
✅	8.1
✅	8.0

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