fix: exclude precision-losing integer-to-float conversions from CastExpr::check_bigger_cast (#23808)

[getChan]

Which issue does this PR close?

• Closes Fix precision loss in CastExpr::check_bigger_cast for integer-to-float conversions #23808.

Rationale for this change

ref. #23807

CastExpr::check_bigger_cast is used to determine whether a cast is a widening (order-preserving) conversion. Currently, it classifies Int32 -> Float32, UInt32 -> Float32, Int64 -> Float64, and UInt64 -> Float64 as widening casts.

However, integer-to-float conversions for 32-bit and 64-bit integers lose precision when values exceed the mantissa bit limit (24 bits for Float32, 53 bits for Float64). For example:
16_777_216_i32 as f32 == 16_777_217_i32 as f32 (both yield 16777216.0f32).

Because distinct integer inputs can collapse to the same float output, these casts are not strictly 1-to-1 (injective) and can break suffix sort key ordering in multi-column ordering analysis (e.g. [CAST(a AS Float32), b]).

What changes are included in this PR?

• Updated CastExpr::check_bigger_cast to exclude precision-losing integer-to-float conversions (Int32/UInt32 -> Float32 and Int64/UInt64 -> Float64).
• Added unit test test_check_bigger_cast_precision_loss to verify precision-losing casts return false while exact conversions (Int16 -> Float32, Int32 -> Float64, etc.) continue to return true.

Are these changes tested?

Yes, new unit test test_check_bigger_cast_precision_loss in cast.rs.

Are there any user-facing changes?

No breaking API changes. Internal optimizer behavior fix.

[codecov-commenter]

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Additional details and impacted files

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