feat: support PostgreSQL ALTER SCHEMA actions

[minleejae]

PostgreSQL schema rename and ownership changes are missing from the statement grammar. Migration tools therefore cannot parse ALTER SCHEMA analytics RENAME TO reporting or inspect an ownership change as a structured statement.

Add AlterSchema with RENAME and OWNER actions, preserving identifier quoting and CURRENT_USER/CURRENT_ROLE/SESSION_USER owner forms. Reuse the existing identifier and contextual-keyword productions, share rendering with StatementDeParser, and connect the statement to visitors, TablesNamesFinder and the PostgreSQL/ALTER validation feature sets.

Tests cover both actions, quoted names, AST mutation, visitor dispatch, statement boundaries, feature validation and incomplete or invalid qualified names. Database authorization and object existence remain database checks.

Syntax reference: PostgreSQL ALTER SCHEMA.

Validation:

• Full Gradle check passed on Java 17, including grammar ambiguity, formatting, static analysis, coverage and the full test suite. JUnit XML totals: 7999 tests, 0 failures/errors, 25 skipped.
• PostgreSQL 17.11: 12 cases (7 valid, 5 invalid). For all 7 valid cases, the original SQL, toString() output and StatementDeParser output executed successfully with matching query results or resulting schema state. Invalid inputs were rejected by the server.

[manticore-projects]

Thank you!