flush deletes by block

[jiangxinmeng1]

What type of PR is this?

• API-change
• BUG
• Improvement
• Documentation
• Feature
• Test and CI
• Code Refactoring

Which issue(s) this PR fixes:

issue #13956 #15249

What this PR does / why we need it:

Flush deletes by block.

[CLAassistant]

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1 out of 2 committers have signed the CLA.

✅ XuPeng-SH
❌ jiangxinmeng1

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