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

[findepi]

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

datafusion/datafusion/common/src/scalar/mod.rs

Lines 2341 to 2354 in 049ca15

	ScalarValue::List(arr) => {
	Self::list_to_array_of_size(arr.as_ref() as &dyn Array, size)?
	}
	ScalarValue::LargeList(arr) => {
	Self::list_to_array_of_size(arr.as_ref() as &dyn Array, size)?
	}
	ScalarValue::FixedSizeList(arr) => {
	Self::list_to_array_of_size(arr.as_ref() as &dyn Array, size)?
	}
	ScalarValue::Struct(arr) => {
	Self::list_to_array_of_size(arr.as_ref() as &dyn Array, size)?
	}
	ScalarValue::Map(arr) => {
	Self::list_to_array_of_size(arr.as_ref() as &dyn Array, size)?

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