[tamnd]

Summary

This PR adds ALTER FUNCTION, ALTER ROUTINE and COMMENT ON FUNCTION for the functions in SQL of the catalog.

Changes

• ALTER FUNCTION changes the options IMMUTABLE, STABLE, VOLATILE, STRICT, CALLED ON NULL INPUT, PARALLEL, COST and ROWS, as AlterFunction does. A second option of the same kind gives 42601 at the place of the option. COST and ROWS must be positive, and ROWS needs a function that returns a set.
• ALTER FUNCTION ... RENAME TO gives the function a new name. A schema that has a function with the new name and the same argument types gives 42723, as IsThereFunctionInNamespace does. The views that call the function get a new text.
• ALTER FUNCTION ... SET SCHEMA moves the function and its pg_depend entry to the new schema. A move to the schema that has the function already does nothing.
• ALTER FUNCTION ... OWNER TO changes proowner, with the checks of AlterObjectOwner_internal for a user that is not a superuser.
• COMMENT ON FUNCTION sets and clears the comment of a function.
• The lookup is the same as for DROP FUNCTION, so the errors for a name that is not unique and for a function that does not exist are the same as in PostgreSQL.
• The command tags are ALTER FUNCTION and ALTER ROUTINE.
• New Catalog::alter_function.

Known differences

• rupg keeps procost and prorows as whole numbers. A value with a fraction gives 0A000.
• SECURITY DEFINER, LEAKPROOF, SUPPORT, SET and RESET give 0A000.
• rupg cannot change or comment on a built-in function. These statements give 0A000.
• The catalog keeps the text of the body of a function. So a new name or a new schema for a function that the body of another function calls gives 0A000.
• ALTER PROCEDURE gives 0A000, because rupg has no procedures yet.

Tests

• New session test alter_function. Its expected output is the output of PostgreSQL 19 for the same script.
• fmt, clippy, the workspace tests and the checks of xtask pass on server1.