Implement ordering serialization for AggregateUdf in datafusion-proto

[alamb]

Is your feature request related to a problem or challenge?

As @jayzhan211 points out on #11013 (comment) the ordering_req field is not supported when serializating/deserializing aggregate udfs

Describe the solution you'd like

Add ordering_req to the serialization / deserializton of aggregateudf and add a test

Describe alternatives you've considered

Here is the code where the ordeirng is ignored when serializing

datafusion/datafusion/proto/src/physical_plan/mod.rs

Lines 480 to 481 in f4e519f

	let _ordering_req: Vec<PhysicalSortExpr> = agg_node.ordering_req.iter()
	.map(|e| parse_physical_sort_expr(e, registry, &physical_schema, extension_codec)).collect::<Result<Vec<_>>>()?;

Additional context

I think technically this may be a regression as builtin functions had proper ordering serialization