Add example of using Expr::field in 37.1.0

[alamb]

I don't intend to merge this, but I want to put it up to illustrate how to use the 37.1.0 API to do this reasonably

Which issue does this PR close?

Part of #10181

Rationale for this change

Some users create expressions outside the context of a query that has an analyzer, etc. Some expressions now can only be used via udfs.

What changes are included in this PR?

Add example of using Expr::field in 37.1.0

Are these changes tested?

Are there any user-facing changes?

[alamb]

This basically inlines the necessary code from

datafusion/datafusion/functions-array/src/rewrite.rs

Lines 151 to 157 in 9560732

	Expr::GetIndexedField(GetIndexedField{
	expr,
	field:GetFieldAccess::NamedStructField{ name },
	}) => {
	let expr = *expr.clone();
	let name = Expr::Literal(name);
	Transformed::yes(get_field(expr, name.clone()))

[alamb]

Here is the proposed public API that should complete this actual issue: #10330