arrow-buffer: add i256::trailing_zeros

[theirix]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

Function trailing_zeros exists for other integer types, and for a wide i128 as well. It's worth adding it.

Describe the solution you'd like

I added a PR with the function

Describe alternatives you've considered

Coding it as an external function - not an ergonomic solution

Additional context

Sister ticket is #8965
Required particularly for DataFusion UDF implementations.

[alamb]

label_issue.py automatically added labels {'arrow'} from #8969