v8.5.6: DM supports MySQL 8.4 (#22505)#22676

ti-chi-bot[bot] merged 3 commits intopingcap:feature/preview-v8.5.6pingcap/docs:feature/preview-v8.5.6from

ti-chi-bot:cherry-pick-22505-to-release-8.5ti-chi-bot/docs:cherry-pick-22505-to-release-8.5Copy head branch name to clipboard