Upgrade ES client to 9.0.0-alpha.3

[afharo]

Summary

Updating the ES client to 9.0.

Resolves #116102

What changes?

Breaking change: body has been removed.

Most of the changes are about bringing all the content inside the body as a root attribute to the API params:

const response = await client.search({
  index: 'test',
-  body: {
    query: {
      match_all: {}
    }
-  }
})

For this reason, enabling the "Hide whitespace changes" option when reviewing is recommended.

Some exceptions to this rule:

• Bulk APIs replace the body array with operations array (direct replacement)
• Index Put Settings API replace body array with settings (direct replacement)
• Msearch replaces the body array with searches array (direct replacement)
• Document Index API replaces body with document (direct replacement)
• Create Repository replaces body with repository (direct replacement)

Because of a known issue in the client (elastic/elasticsearch-js#2584), there's still an escape hatch to send data in the body in case the specific use case requires it via // @ts-expect-error elasticsearch@9.0.0 https://github.com/elastic/elasticsearch-js/issues/2584, but it shouldn't be abused because we lose types. In this PR we've used it in those scenarios where we reuse the response of a GET as the body of a PUT/POST.

Other changes

• estypes can be imported from the root of the library as import type { estypes } from '@elastic/elasticsearch';
• estypesWithBody have been removed
• requestTimeout's 30s default has been removed in the client. This PR explicitly adds the setting in all client usages.

Identify risks

• The client places unknown properties as querystring, risking body params leaking there, and causing 400 errors from ES => Solved by forcing body usage there via // @ts-expect-error elasticsearch@9.0.0 https://github.com/elastic/elasticsearch-js/issues/2584. The next version of the client will address this.
• We need to run the MKI tests to make sure that we're not breaking anything there => https://elastic.slack.com/archives/C04HT4P1YS3/p1739528112482629?thread_ts=1739480136.231439&cid=C04HT4P1YS3

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[github-actions]

It looks like this PR modifies one or more .asciidoc files. These files are being migrated to Markdown, and any changes merged now will be lost. See the migration guide for details.