[C++][R] Strptime should detect invalid formats

[asfimport]

As discussed here we want C++ to report invalid strptime formats to avoid having to implement this logic in multiple places. Once that is in place (if it's not yet) we should add tests for this error in R. Currently an invalid format used in R will simply return an array of NAs.

Reporter: Rok Mihevc / @rok
Watchers: Rok Mihevc / @rok

_{Note: This issue was originally created as ARROW-17218. Please see the migration documentation for further details.}