refactor(sql): improve agg index rewrite matching

[forsaken628]

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

Summary

This PR refactors aggregating index rewrite to use structural expression matching instead of string-based matching.

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 

[github-actions]

🤖 CI Job Analysis

Workflow: 23342902507

📊 Summary

• Total Jobs: 86
• Failed Jobs: 11
• Retryable: 0
• Code Issues: 11

❌ NO RETRY NEEDED

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

🔍 Job Details

• ❌ linux / test_unit: Not retryable (Code/Test)
• ❌ linux / sqllogic / standalone_minio (query, http, native): Not retryable (Code/Test)
• ❌ linux / sqllogic / standalone_minio (query, hybrid, native): Not retryable (Code/Test)
• ❌ linux / sqllogic / standalone_minio (query, http, parquet): Not retryable (Code/Test)
• ❌ linux / sqllogic / standalone_minio (query, hybrid, parquet): Not retryable (Code/Test)
• ❌ linux / sqllogic / cluster (query, 4c, hybrid): Not retryable (Code/Test)
• ❌ linux / sqllogic / standalone (query, 4c, http): Not retryable (Code/Test)
• ❌ linux / sqllogic / cluster (query, 4c, http): Not retryable (Code/Test)
• ❌ linux / sqllogic / standalone (standalone, 2c, http): Not retryable (Code/Test)
• ❌ linux / sqllogic / standalone (query, 4c, hybrid): Not retryable (Code/Test)
• ❌ linux / sqllogic / standalone (standalone, 2c, hybrid): Not retryable (Code/Test)

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🤖 About

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