fix: unparse for subqueryalias

[chenkovsky]

Which issue does this PR close?

• Closes Unparse SubqueryAlias with the pushdown TableScan fail #13272.

Rationale for this change

the qualifier is incorrect for subqueryalias when unparsing.

What changes are included in this PR?

wrap with subqueryalias if alias is passed when unparsing.

Are these changes tested?

Unittest

Are there any user-facing changes?

No

[alamb]

Thank you @chenkovsky

[alamb]

I think you can write this a bit more concisely by unwrapping the error earlier if you wanted:

Something like

Suggested change

	let ret = Self::unparse_table_scan_pushdown(
	&subquery_alias.input,
	Some(subquery_alias.alias.clone()),
	already_projected,
	)
	);
	if let Some(alias) = alias {
	if let Ok(Some(plan)) = ret {
	let plan = LogicalPlanBuilder::new(plan).alias(alias)?.build()?;
	return Ok(Some(plan));
	}
	}
	)?;
	if let Some(alias) = alias {
	let plan = LogicalPlanBuilder::new(plan).alias(alias)?.build()?;
	return Ok(Some(plan));
	}
	Ok(ret)

[alamb]

I parsed this with some structure and it looks right to me

Thanks @chenkovsky

 "SELECT 
   customer_view.c_custkey, 
   customer_view.c_name, 
   customer_view.custkey_plus 
   FROM 
   (SELECT 
     customer.c_custkey, 
     (CAST(customer.c_custkey AS BIGINT) + 1) AS custkey_plus, 
     customer.c_name 
     FROM 
     (SELECT 
       customer.c_custkey, 
       customer.c_name 
       FROM customer AS customer
       ) AS customer
       ) AS customer_view");

[goldmedal]

Thanks @chenkovsky and @alamb for reviewing 👍