Fix ALTER deparser dispatch for inactive column metadata

[minleejae]

Purpose

Make ALTER deparsing follow the same active body as toString(), including when callers mutate an action or retain metadata from a previous operation. A drop action changed to ALTER COLUMN id RESTART, with a leftover SET DEFAULT entry, currently renders the identity action through toString() but renders the unrelated default through StatementDeParser.

Current design (As-is)

getColumnDefaults() infers an active default action from base-class fields, while subclasses choose their own rendering paths. The deparser also treats any stored column-definition list as active. These independent decisions let inactive metadata replace the actual statement body and send unrelated expressions to a custom visitor.

Target design (To-be)

• Share the base default/visibility body decision between rendering and default lookup through usesColumnActionBody().
• Expose hasActiveColumnDefinitions() and have AlterDeParser use that decision instead of mere list presence.
• Implement both decisions for dedicated ALTER bodies. Preserve the established priority of defaults, constraint headers, renames, drop variants, table options and column definitions.
• Keep stored metadata accessible and preserve custom expression rewriting for the active body, including its common tail exactly once.

The usage guide documents the distinction between stored and active metadata. Custom subclasses that replace appendBody() should override the matching dispatch hooks when changing these rules. This change does not add SQL syntax or replace the index/constraint model.

CI follow-up

The macOS Maven job failed before the traversal benchmark started: parsing its generated 30,000-CTE SQL exceeded CCJSqlParserUtil's parser timeout (JSQLParserException: Time out occurred, caused by TimeoutException). The fixture now builds the equivalent AST directly. It retains 30,000 CTE aliases, 30,000 table references and the two-second traversal assertion; parser and traversal timeout limits are unchanged.

Validation

• After the CI follow-up: all 107 TablesNamesFinderTest cases pass locally in both Gradle and Maven on Java 17, including the unchanged-size traversal performance check. The updated head a7ea55dd passes grammar checks, Gradle and Maven on Ubuntu/Windows/macOS, and Codacy. Deployment-only jobs are skipped as expected for a PR.

• Java 17 Gradle spotlessApply check after rebasing onto master (066f581e): 10,061 tests, 10,036 passed, 25 skipped, zero failures/errors. Grammar, formatting, Checkstyle, PMD, SpotBugs and coverage checks pass.

• 21 new regression cases cover the identity/default mismatch, PostgreSQL/MySQL editable defaults, custom expression visitors, TYPE USING, common-tail rendering, nine dedicated action bodies and competing base-body metadata. The focused set of 54 new/existing rendering/default tests passes.

• Additional cached PMD default-complexity and field-placement comparisons introduce no new method violations.

• Applying both remaining follow-ups (Fix ALTER deparser dispatch for inactive column metadata #2770 and Separate ALTER key definitions from column drop targets #2771) together on current master produces exactly the same Git tree as the previously tested eight-PR integration. That integration passed the complete Java 17 Gradle check: 10,079 tests, 10,054 passed, 25 skipped, zero failures/errors.

• Replayed 882 previously DB-validated DDL fixtures against that integrated build: 875 pass with unchanged SQL output and reparsing; the same seven existing parse gaps remain. Nine statements intentionally expose raw ColumnOption nodes in the AST node-type set. No other result differences except generated grammar source locations; no fresh database execution.

This is an independent master-based follow-up (066f581e), related to the editable identity API in #2768.

[manticore-projects]

Please resolve many conflicts.