chore: search-index-consumer - handle version conflict race condition [CHI-3702]

[gpaoloni]

Description

This PR

• Refactors ElasticSearch client: index and update operations return a result type wrapping the actual response, consolidating with the changes introduced in chore: improve error handling around ES deletes [CHI-3516] #984.
• Refactors search index consumer lambda: Introduces retries for index and update operations for the cases where there's a race condition, as described in the linked ticket below.

Checklist

• Corresponding issue has been opened
• New tests added
• Feature flags / configuration added

Verification steps

AFTER YOU MERGE

1. Cut a release tag using the GitHub workflow. Wait for it to complete and notify in the #aselo-deploys Slack channel.
2. Comment on the ticket with the release tag version AND any additional instructions required to configure an environment to test the changes.
3. Only then move the ticket into the QA column in JIRA

You are responsible for ensuring the above steps are completed. If you move a ticket into QA without advising what version to test, the QA team will assume the latest tag has the changes. If it does not, the following confusion is on you! :-P

[stephenhand]

LGTM