fix: fix count rewrite in agg index

[ariesdevil]

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Summary

count(col) will be rewritten to count() if col is NOT nullable, as create agg index will rewrite statement and don't know the col's datatype, we will provide both count(col) and count() for agg index, make query rewrite with agg index happy.

Fixes #14249

Tests

• Unit Test
• Logic Test
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• 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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