ddl: Fix default value filling with finer granularity (#10682)#10688

JaySon-Huang merged 5 commits into

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ti-chi-bot:cherry-pick-10682-to-release-7.5-20260128-v7.5.5ti-chi-bot/tiflash:cherry-pick-10682-to-release-7.5-20260128-v7.5.5Copy head branch name to clipboard