Converge StructFunc and NamedStructFunc to one func #11204

Is your feature request related to a problem or challenge?

We currently have two func StructFunc and NamedStructFunc, where StructFunc is actually NamedStructFunc with default naming c1, c2... cn

I think it is easier to maintain the code if we have only one single struct function. If the name of field is not given, we fallback to default name "c{index}"

Describe the solution you'd like

Simplify the divergence of these two functions with minimum breaking change.

Also, converge create_named_struct and create_struct to one in sqltorel

Describe alternatives you've considered

Keep as it is

Additional context

No response
This also help #9820 easier to implement