[Runtime field editor] Fix preview error when not enough privileges

[sebelga]

There is a current limitation in the ES Painless _execute API that requires too many privileges (cluster privileges [manage,all]). This is a problem when previewing a runtime field script.

This PR brings a temporary fix to this problem by not using the _execute API but the _search API.

How to test

• Create a new role with only the read and view_index_metadata privilege on one of the indices
• Assign a new user to that role and log into Kibana with that user
• Navigate to the index pattern management app, select your index pattern and create a new field
• Write a simple script (e.g. emit('hello');). --> You should see the preview of the script in the panel.
• Change the script with emit(123); --> you should get a casting error

Fixes #114034
Fixes #114036
Fixes https://github.com/elastic/infra/issues/31927

[elasticmachine]

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

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 38e49d7
• Storybooks Preview

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
indexPatternFieldEditor	151.5KB	151.5KB	+13.0B

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
indexPatternFieldEditor	19.0KB	19.0KB	+26.0B

History

• 💔 Build #161331 failed cf2efdc
• 💔 Build #161092 failed 17a4032

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[mattkime]

code looks good and works well!

[sebelga]

Thanks for the review @mattkime !