[Backport 2.x] Change filenames for IndexMetadata and Manifest [#10557]#10700

shwetathareja merged 2 commits intoopensearch-project:2.xopensearch-project/OpenSearch:2.xfrom

dhwanilpatel:backport_file_name_changesdhwanilpatel/OpenSearch-1:backport_file_name_changesCopy head branch name to clipboard