Add support for BinaryView in arrow_string::length

[Omega359]

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

Add support for binary view in the length fn. This was brought up in a code review in #6345

Describe the solution you'd like

Code, tests added for calculating length for binary view.

Describe alternatives you've considered

Do not implement.

Additional context

[Omega359]

take

[alamb]

label_issue.py automatically added labels {'arrow'} from #6345