fix(io): correct BitmapReader BITMAP_LENGTH from 1024 to 8192

[zhang2014]

I hereby agree to the terms of the CLA available at: https://docs.databend.com/dev/policies/cla/

Summary

fix(io): correct BitmapReader BITMAP_LENGTH from 1024 to 8192

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):

---

This change is 

[github-actions]

🤖 CI Job Analysis

Workflow: 24287126571

📊 Summary

• Total Jobs: 87
• Failed Jobs: 1
• Retryable: 0
• Code Issues: 1

❌ NO RETRY NEEDED

All failures appear to be code/test issues requiring manual fixes.

🔍 Job Details

• ❌ linux / sqllogic / standalone_iceberg_tpch: Not retryable (Code/Test)

---

🤖 About

Automated analysis using job annotations to distinguish infrastructure issues (auto-retried) from code/test issues (manual fixes needed).