[ML] Fix bug with fields.yml not defined, add jest tests for new transform installation mechanism in Fleet

[qn895]

Summary

Follow up of #140046. This PR adds jest tests for the new transform installation mechanism in Fleet. It also fixes a bug with when fields.yml or mappings are not defined.

Checklist

Delete any items that are not applicable to this PR.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• Any UI touched in this PR is usable by keyboard only (learn more about keyboard accessibility)
• Any UI touched in this PR does not create any new axe failures (run axe in browser: FF, Chrome)
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• This renders correctly on smaller devices using a responsive layout. (You can test this in your browser)
• This was checked for cross-browser compatibility

Risk Matrix

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Before closing this PR, invite QA, stakeholders, and other developers to identify risks that should be tested prior to the change/feature release.

When forming the risk matrix, consider some of the following examples and how they may potentially impact the change:

Risk	Probability	Severity	Mitigation/Notes
Multiple Spaces—unexpected behavior in non-default Kibana Space.	Low	High	Integration tests will verify that all features are still supported in non-default Kibana Space and when user switches between spaces.
Multiple nodes—Elasticsearch polling might have race conditions when multiple Kibana nodes are polling for the same tasks.	High	Low	Tasks are idempotent, so executing them multiple times will not result in logical error, but will degrade performance. To test for this case we add plenty of unit tests around this logic and document manual testing procedure.
Code should gracefully handle cases when feature X or plugin Y are disabled.	Medium	High	Unit tests will verify that any feature flag or plugin combination still results in our service operational.
See more potential risk examples

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[elasticmachine]

Pinging @elastic/ml-ui (:ml)

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[qn895]

@elasticmachine merge upstream

[nchaulet]

I am not the most familiar with that feature but tests looks good to me 🚀

[qn895]

@elasticmachine merge upstream

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 2266d7e

Metrics [docs]

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
fleet	62	63	+1

Total ESLint disabled count

id	before	after	diff
fleet	70	71	+1

History

• 💚 Build #77627 succeeded d150e2d
• 💚 Build #76911 succeeded ddf538a
• 💔 Build #76675 failed cf33599

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

cc @qn895

[qn895]

@elasticmachine merge upstream

[hop-dev]

Thanks for these tests and the fix, looks good to me 🚀

Kyle is on leave this week so won't be able to review.

[kibanamachine]

💚 All backports created successfully

Status	Branch	Result
✅	8.5

Note: Successful backport PRs will be merged automatically after passing CI.

Questions ?

Please refer to the Backport tool documentation

[kibanamachine]

💚 All backports created successfully

Status	Branch	Result
✅	8.5

Note: Successful backport PRs will be merged automatically after passing CI.

Questions ?

Please refer to the Backport tool documentation