Advanced Search: Allow bulk cron worker parallel processing

What does this MR do and why?

Currently, we use 16 sharded zsets to track all the updates for Advanced Search integration. One worker for initial queue ElasticIndexInitialBulkCronWorker and one for incremental ElasticIndexBulkCronWorker.

This MR allows these shards to be processed independently when the parallel_bulk_cron_worker feature flag is enabled.

Screenshots or screen recordings

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #340963 (closed)