Unify column option storage and mutation contracts

[minleejae]

Purpose

Give callers one predictable way to inspect and edit CREATE/ALTER column options. Today getColumnSpecs().add(...) changes SQL for raw specifications but silently edits a detached copy when structured options are present.

Current design (As-is)

ColumnDefinition has mutually exclusive columnSpecs and columnOptions lists. The grammar collects both token and node representations, then discards the nodes for raw-only definitions. List ownership and getter mutation behavior depend on which representation is active.

Target design (To-be)

• Keep one ordered List<ColumnOption>, retaining opaque specifications as Kind.OTHER nodes. Remove the duplicate field and grammar token collection.
• Return an unmodifiable token snapshot from getColumnSpecs() in every mode. Use addColumnSpecs(...) to append, setColumnSpecs(...) to explicitly replace all options with raw text, or edit the mutable nodes/list returned by getColumnOptions().
• Copy incoming token lists and option-list membership while preserving the identity of mutable child nodes. Appending raw tokens preserves structured expressions, references and visitor access; raw text is never automatically parsed.
• Preserve unset versus explicitly empty options. Keep constructors independent of overridable setters, and document migration examples and ownership contracts.

API migration: mutating getColumnSpecs() now throws UnsupportedOperationException. Raw-only options are also visible through getColumnOptions(); ALTER definitions without options expose an empty option list. Consumers should inspect node kinds instead of using list nullness to detect structured options. SQL acceptance and rendering are unchanged.

Validation

• Java 17 Gradle spotlessApply check: 9,962 tests, 9,937 passed, 25 skipped, zero failures/errors. Grammar, formatting, Checkstyle, PMD, SpotBugs and coverage checks pass.

• 11 new regression cases cover raw/typed CREATE and ALTER definitions, snapshots, input ownership, live child edits, visitor/deparser behavior, replacement, null/empty values, fluent builders and subclass construction. The constructor regression fails against the version that called an overridable setter.

• Additional cached PMD checks with default NPath/cyclomatic-complexity and field-placement thresholds: zero violations before and after in the changed production class.

• A local integration of all eight follow-ups (Use one foreign-key state in ALTER TABLE #2764–Separate ALTER key definitions from column drop targets #2771), with overlapping ALTER edits resolved, passes 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 follow-up to #2747, based on master (cdbaf1ad).