fix(executor): enable backpressure for union all

[zhang2014]

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Summary

fix(executor): enable backpressure for union all

related #16380

Tests

• [ ] Unit Test
• [x] Logic Test
• [x] 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
• [x] Refactoring
• [ ] Performance Improvement
• [ ] Other (please describe):

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This change is 

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Docker Image for PR

• tag: pr-16388-bfd819c-1725446050

note: this image tag is only available for internal use, please check the internal doc for more details.

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Docker Image for PR

• tag: pr-16388-bfd819c-1725447491

note: this image tag is only available for internal use, please check the internal doc for more details.

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ClickBench Report

• hits: https://benchmark.databend.com/clickbench/pr/16388/10699307188/hits.html
• internal: https://benchmark.databend.com/clickbench/pr/16388/10699307188/internal.html
• load: https://benchmark.databend.com/clickbench/pr/16388/10699307188/load.html
• tpch: https://benchmark.databend.com/clickbench/pr/16388/10699307188/tpch.html

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ClickBench Report

• hits: https://benchmark.databend.com/clickbench/pr/16388/10699452152/hits.html
• internal: https://benchmark.databend.com/clickbench/pr/16388/10699452152/internal.html
• load: https://benchmark.databend.com/clickbench/pr/16388/10699452152/load.html
• tpch: https://benchmark.databend.com/clickbench/pr/16388/10699452152/tpch.html