feat: http handler support set variable.

[youngsofun]

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Summary

part of #16135

the last versions of drivers should be able to work directly.
bendsql-cli seems to have problem when meeting $a.

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

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This change is 

[youngsofun]

@sundy-li plz review again