[7.x] [ML] Improve support for script and aggregation fields in anomaly detection jobs (#81923)

[qn895]

Backports the following commits to 7.x:

• [ML] Improve support for script and aggregation fields in anomaly detection jobs ([ML] Improve support for script and aggregation fields in anomaly detection jobs #81923)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 005aaa2

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
ml	1564	1565	+1

Async chunks

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

id	before	after	diff
ml	5.2MB	5.2MB	+5.9KB

Distributable file count

id	before	after	diff
default	43198	43199	+1

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@elasticmachine merge upstream