[C++] Implement casting to dictionary type (dictionary_encode as a cast) #33171
Description
We can cast dictionary(string, X) to string, but not the other way around.
> Array$create(c("a", "b"))$cast(dictionary(int32(), string()))
Error: NotImplemented: Unsupported cast from string to dictionary using function cast_dictionary
/Users/willjones/Documents/arrows/arrow/cpp/src/arrow/compute/function.cc:249 func.DispatchBest(&in_types)
> Array$create(as.factor(c("a", "b")))$cast(string())
Array
<string>
[
"a",
"b"
]Reporter: Will Jones / @wjones127
Related issues:
Note: This issue was originally created as ARROW-17963. Please see the migration documentation for further details.