[R] Add binding for case_when()

[asfimport]

ARROW-13064 adds a case_when kernel that works like a SQL CASE WHEN expression. This allows us to implement a binding for the dplyr function case_when().

Reporter: Ian Cook / @ianmcook
Assignee: Ian Cook / @ianmcook

Related issues:

• [C++] Add a general "if, ifelse, ..., else" kernel ("CASE WHEN") (depends upon)

PRs and other links:

• GitHub Pull Request #10737

_{Note: This issue was originally created as ARROW-13200. Please see the migration documentation for further details.}

[asfimport]

Ian Cook / @ianmcook:
Issue resolved by pull request 10737
#10737