[GRPC][Joining queries] Implement GRPC Nested query, fix InnerHits, and bump to 0.19.0 protobufs#19453

cwperks merged 10 commits intoopensearch-project:mainopensearch-project/OpenSearch:mainfrom

karenyrx:0.18.0_nestedkarenyrx/OpenSearch:0.18.0_nestedCopy head branch name to clipboard