[R] Update case_when() binding to match changes in dplyr

https://github.com/tidyverse/dplyr/pull/6300 introduced a change to the case_when() API.

Most importantly:

There is a new .default argument that is intended to replace usage of TRUE ~ default_value

There are also new arguments .ptype and .size.

There are a few other changes also, highlighted in the dplyr NEWS.md file

Also see https://twitter.com/dvaughan32/status/1542942862077317121.

We should update the case_when() binding in the arrow R package to be consistent with its new behaviors in dplyr, or to throw an error if the user passes new arguments that we cannot handle consistently with dplyr.