[R] Add bindings for ifelse() and if_else()

[asfimport]

ARROW-10640 adds an if_else kernel to the C++ library. Add R bindings so users can call ifelse() or if_else() (the stricter dplyr variant) in dplyr verbs. I believe the C++ kernel requires the second and third arguments to have the same types, just like dplyr::if_else().

Reporter: Ian Cook / @ianmcook
Assignee: Nicola Crane / @thisisnic

Related issues:

• [C++] An "if_else" kernel to combine two arrays based on a mask (depends upon)

PRs and other links:

• GitHub Pull Request #10724

_{Note: This issue was originally created as ARROW-12964. Please see the migration documentation for further details.}

[asfimport]

Neal Richardson / @nealrichardson:
Issue resolved by pull request 10724
#10724