fix(parser): allow VERSION in ALTER column clauses

[minleejae]

What

• Allow the non-reserved VERSION keyword to be used as a column identifier in the restricted KeywordOrIdentifier production used by ALTER TABLE.
• Allow VERSION in CreateParameter, which currently captures PostgreSQL USING expressions attached to ALTER COLUMN ... TYPE.
• Add parse/deparse regressions for DROP COLUMN version and ALTER COLUMN version TYPE ... USING version::....

Why

VERSION is already declared as a non-reserved keyword, but two narrower legacy productions do not accept it. As a result, valid PostgreSQL statements such as these fail on the current master branch:

ALTER TABLE test_table DROP COLUMN version, DROP COLUMN other_column;
ALTER TABLE test_table ALTER COLUMN version TYPE VARCHAR(32) USING version::VARCHAR(32);

PostgreSQL allows non-reserved keywords to be used as identifiers. This change is intentionally limited to the two productions exercised by these statements and introduces no new JavaCC choice conflicts.

PostgreSQL keyword reference: https://www.postgresql.org/docs/current/sql-keywords-appendix.html

Testing

• ./gradlew check
• Added both statements to AlterTest and verified parse/deparse round trips.

AI assistance

OpenAI Codex was used to identify the regression from a PostgreSQL ALTER corpus, prepare the focused grammar change, and run validation. The generated change and tests were reviewed against the PostgreSQL documentation.

[manticore-projects]

thank you!!