Prevent request corruption by avoiding failing entire bulk request on single shard rejection from shard backpressure#20727

varunbharadwaj wants to merge 2 commits intoopensearch-project:mainopensearch-project/OpenSearch:mainfrom

varunbharadwaj:vb/shardindexpressurevarunbharadwaj/OpenSearch:vb/shardindexpressureCopy head branch name to clipboard