[Upgrade Assistant] Fix ml model upgrade status check

[sabarasaba]

Fixes #121313

Summary

This PR uses a newly implemented api from ES (elastic/elasticsearch#81641) in order to have a more accurate representation of the model snapshot upgrade. Nothing should be noticeable different from before, except that we now pull the status from a different api endpoint.

How to test

1. Start elasticsearch with yarn es snapshot --license=trial -E path.data=./data-6.8.20 and kibana with yarn start. You can use this snapshot data-6.8.20.zip I created that contains a ML deprecation that requires upgrading.
2. Navigate to Stack Management -> Upgrade Assistant -> ES deprecations
3. Verify that upgrading the ML deprecation in the table follows the usual flow.

Note: when this PR is merged, I'll create a new one for getting this change into main and 8.x

[elasticmachine]

Pinging @elastic/kibana-stack-management (Team:Stack Management)

[kibana-ci]

💚 Build Succeeded

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• Commit: 35b687f
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Metrics [docs]

✅ unchanged

History

• 💔 Build #14166 failed 8980a3b
• 💔 Build #14138 failed 86f48b9

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

cc @sabarasaba

[sabarasaba]

Closing in favour of #121646 which points to 7.17