[v25.2.x] iceberg: Push Parquest column stats to Iceberg manifests

Backport https://github.com/redpanda-data/redpanda/pull/30704 to branch v25.2.x. This issue was created as a placeholder because the original PR's commit(s) could not be automatically cherry-picked. Here are the commands to execute: ``` git checkout v25.2.x git checkout -b manual-backport-30704-v25.2.x-202 git cherry-pick -x 7f833530e9 b4e8232b4e git push origin manual-backport-30704-v25.2.x-202 gh pr create \ --title "[v25.2.x] iceberg: Push Parquest column stats to Iceberg manifests" \ --base "v25.2.x" \ --label "kind/backport" \ --head "manual-backport-30704-v25.2.x-202" \ --draft \ --repo "redpanda-data/redpanda" \ --milestone "v25.2.x-next" \ --body "Backport of PR https://github.com/redpanda-data/redpanda/pull/30704 "