Ark: Coercion methods into `RObject` vectors should catch OOM errors

[lionel-]

The allocVector() calls in vector coercion methods (e.g. https://github.com/posit-dev/amalthea/blob/f16a0137ed416330658ffd242c2b8c7b5792f045/crates/harp/src/object.rs#L759) might throw an R error over our Rust stack. We should run these in a r_try_catch(), probably via a wrapper that returns a Result.