[DOC] Add documentation for retry settings for Remote reindex

[ankitkala]

What do you want to do?

• Request a change to existing documentation
• Add new documentation
• Report a technical problem with the documentation
• Other

Tell us about your request. Provide a summary of the request and all versions that are affected.
We've introduced 2 new setting (for all newer versions starting with 2.13) which allows users to configure the retry mechanism for remote reindex.

• reindex.remote.retry.initial_backoff: Backoff time for retries with default as 500ms. Subsequent retries will do exponential backoff based on initial backoff time.
• reindex.remote.retry.max_count: Max retry count with default value of 15 retries

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.
https://github.com/opensearch-project/OpenSearch/pull/12561/files

[hdhalter]

@ankitkala - Can you please submit a doc PR for this update? Thanks!