refactor(query): rewrite equivalent function calls as casts

[forsaken628]

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Summary

• Resolve cast functions from the actual Expr::Cast execution path instead of inferring equivalence from function names.
• Rewrite a function call to CastExpr only when its canonical function, parameters, argument type, and return type exactly match the resolved cast implementation.
• Reuse the same resolved function in cast evaluation and domain inference, including nullable, decimal, Variant/JSON, and try-cast cases.

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):

AI assistance

• AI usage: An AI coding agent assisted with implementation.
• Responsible human: @forsaken628
• The responsible human has read every line of this diff and can explain each change

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