Add support for the "r+" datatype in the C Data interface / RunArray

[notfilippo]

Describe the bug

C Data interface error: The datatype ""+r"" is still not supported in Rust implementation

To Reproduce

let value_data = PrimitiveArray::<Int8Type>::from_iter_values([10_i8, 11, 12, 13, 14, 15, 16, 17]);

// Construct a run_ends array:
let run_ends_values = [4_i32, 6, 7, 9, 13, 18, 20, 22];
let run_ends_data = PrimitiveArray::<Int32Type>::from_iter_values(run_ends_values.iter().copied());

// Construct a run ends encoded array from the above two
let ree_array = RunArray::<Int32Type>::try_new(&run_ends_data, &value_data).unwrap();

// export it
let (array, schema) = to_ffi(&ree_array.to_data())?;

// (simulate consumer) import it
let data = unsafe { from_ffi(array, &schema) }?;

Expected behavior

The RunArray can be converted to / from the C data interface.

[tustvold]

label_issue.py automatically added labels {'arrow'} from #5632