Refactor iszero() and isnan() to accept all numeric types

[kumarUjjawal]

Which issue does this PR close?

• Closes Refactor iszero() and isnan() to accept all numeric types #20089

Rationale for this change

iszero() and isnan() previously accepted “numeric” inputs by implicitly coercing them to Float64, adding unnecessary casts and work for integer/decimal inputs.

What changes are included in this PR?

• Updated iszero() and isnan() signatures to accept TypeSignatureClass::Numeric without implicit float coercion.
• Refactored iszero() implementation to evaluate zero checks directly for integers, unsigned integers, floats, and decimals.
• Refactored isnan() implementation to compute is_nan only for float types and return false for all other numeric types and reduced non-float array handling to use unary kernels instead of manual iteration.
• Added sqllogictest

Are these changes tested?

Yes

Are there any user-facing changes?

No

[Jefffrey]

For decimal is_zero we need to consider the scale
E.g. negative scale can never be zero

Edit: actually maybe I'm wrong 🤔