[Backport 2.x] Add ThreadContextPermission for stashAndMergeHeaders and stashWithOrigin#15049

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

cwperks:backport-15039-to-2.xcwperks/OpenSearch:backport-15039-to-2.xCopy head branch name to clipboard