fix(exasol)!: qualified select list with "LOCAL"

[nnamdi16]

What motivated this PR?

Exasol requires the LOCAL qualifier when referencing column aliases in GROUP BY, HAVING, WHERE, and the SELECT list.
The previous implementation only handled GROUP BY, WHERE, and HAVING, but did not apply LOCAL to alias references inside the SELECT list.
This PR adds the missing behavior in accordance with Exasol’s documented rules:
https://docs.exasol.com/db/latest/sql/select.htm

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What was incorrect in the existing logic?

Given a query such as:

SELECT YEAR(current_date) AS current_year,
       current_year + 1 AS next_year

The transpiler did not rewrite current_year to LOCAL.current_year inside the SELECT list.
Since Exasol requires LOCAL.alias for any alias referenced within the same SELECT clause, the generated SQL was invalid.

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How does this PR resolve the issue?

The PR extends the existing alias-handling transformation so that:

• Alias references inside the SELECT list are detected, and
• They are rewritten as LOCAL.alias, consistent with Exasol requirements.

This makes alias resolution behavior complete and aligned across SELECT, GROUP BY, HAVING, and WHERE.

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Documentation & Semantic Notes

Exasol’s rules for alias qualification are documented here:
https://docs.exasol.com/db/latest/sql/select.htm

The semantics are fully preserved — the PR does not change query meaning.
It only adds the required LOCAL prefix in the SELECT list so that transpiled queries execute correctly on Exasol.

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[VaggelisD]

The output SQL is identical to input, we don't need to redefine it

Suggested change

	self.validate_identity(
	'SELECT a_year AS a_year FROM "LOCAL" GROUP BY "LOCAL".a_year',
	'SELECT a_year AS a_year FROM "LOCAL" GROUP BY "LOCAL".a_year',
	)
	self.validate_identity(
	'SELECT a_year AS a_year FROM "LOCAL" GROUP BY "LOCAL".a_year'
	)

[VaggelisD]

Does the input query work on Exasol? If not, we shouldn't be adding validate_identity that the input SQL does not work on that engine, those should be done through validate_all as you have done for DBX

[VaggelisD]

Afaict this can be simplified to:

Suggested change

	alias_node = sel.args.get("alias")
	if alias_node and alias_node.name:
	seen_aliases[alias_node.name] = bool(alias_node.args.get("quoted"))
	seen_aliases[sel.alias] = bool(alias_node.args.get("quoted"))