fix(optimizer): Quotation issue in canonicalize_internal_names

[fivetran-kwoodbeck]

canonicalize_internal_names was quoting unqualified base column references when its name happened to match the top level output alias. This produced inconsistent identifier quoting in the canonical output. This violates the rule that base-table column references are part of the data contract and must be preserved verbatim.

The fix narrows the rewrite so it only fires when the alias is actually being renamed.

Query:

SELECT a AS a, b AS c, d AS renamed FROM cat.db.t WHERE a > b AND b > 0 AND d < 0

Stage	Result
Before	SELECT "a" AS a, b AS c, d AS renamed FROM cat.db.t AS "_t0" WHERE "a" > b AND b > 0 AND d < 0
After	SELECT a AS a, b AS c, d AS renamed FROM cat.db.t AS "_t0" WHERE a > b AND b > 0 AND d < 0

[github-actions]

SQLGlot Integration Test Results

✅ All tests passed

Comparing:

• this branch (sqlglot:optimizer/bug-canonicalize-internal-names-alias-collision @ sqlglot efe3c32)
• baseline (main @ sqlglot 17f7870)

Overall

main: 192428 total, 153523 passed (pass rate: 79.8%)

sqlglot:optimizer/bug-canonicalize-internal-names-alias-collision: 180234 total, 142378 passed (pass rate: 79.0%)

Transitions:
No change

Dialect pair changes: 0 previous results not found, 3 current results not found

✅ All tests passed

[georgesittas]

@fivetran-kwoodbeck how did you test this? I don't see any issue:

>>> from sqlglot import parse_one
>>> from sqlglot.optimizer.qualify import qualify
>>> from sqlglot.optimizer.canonicalize_internal_names import canonicalize_internal_names
>>>
>>> sql = "SELECT a AS a, b AS c, d AS renamed FROM cat.db.t WHERE a > b AND b > 0 AND d < 0"
>>> ast = parse_one(sql)
>>> qualified = qualify(ast, schema={"cat": {"db": {"t": {"a": "int", "b": "int", "d": "int"}}}})
>>> canonicalized = canonicalize_internal_names(qualified)
>>>
>>> canonicalized.sql()
'SELECT "_t0"."a" AS "a", "_t0"."b" AS "c", "_t0"."d" AS "renamed" FROM "cat"."db"."t" AS "_t0" WHERE "_t0"."a" > "_t0"."b" AND "_t0"."b" > 0 AND "_t0"."d" < 0'