Optimize ColumnarValue::into_array / ScalarValue::to_array / ScalarValue::to_array_of_size #13754

When implementing functions, ColumnarValue::into_array / ScalarValue::to_array / ScalarValue::to_array_of_size are useful to reduce code complexity and denominate input arguments in terms of an array (either full-sized or 1-sized).

The code to handle scalars of structural types is

it's not optimized for the common case of input array (the scalar) being of length 1 and requested length also being 1.
In such case it could probably be reduced to Arc::clone