gcd benchmarks pass number_rows: 0 for 100k-row inputs #26297

Describe the bug

All three benchmarks in functions/benches/math_expressions/gcd.rs pass number_rows: 0 in ScalarFunctionArgs, including "gcd both array" and "gcd array and scalar", whose array inputs have 100,000 rows. The sibling lcm.rs benchmark passes number_rows: n_rows. A UDF that sizes its output or expands scalars from number_rows will not do the work the benchmark claims to measure.

Every gcd benchmark also uses the copy-pasted message .expect("date_bin should work on valid values").

To Reproduce

Read gcd.rs lines 56, 77 and 98 (number_rows: 0) and compare with lcm.rs line 55 (number_rows: n_rows).

Expected behavior

• Pass number_rows: n_rows for the benchmarks with array inputs (and 1 for scalar-scalar).
• Change the expect messages to "gcd should work on valid values".

Additional context

to_char.rs (L144-L341), gcd.rs and lcm.rs repeat the same bench_function + ScalarFunctionArgs boilerplate seven times, which is how this drift happened. A small shared helper that takes the UDF, args, number_rows and return type would prevent it. That part is optional.

This is a small, self-contained change and a good first issue. Line references are pinned to commit 0d79252.