BUG #19559: ALTER TABLE SET EXPRESSION / ALTER TYPE fails on columns referenced by a property graph

The following bug has been logged on the website:

Bug reference: 19559
Logged by: Fredrik Svensson
Email address: svenna01(at)gmail(dot)com
PostgreSQL version: 19beta2
Operating system: Linux (Debian trixie, official postgres:19beta2
Description:

On 19beta2:

CREATE TABLE t (id int PRIMARY KEY, a int, b int,
s int GENERATED ALWAYS AS (a + b) STORED);
ALTER TABLE t ALTER COLUMN s SET EXPRESSION AS (a - b); -- ok
CREATE PROPERTY GRAPH g
VERTEX TABLES (t KEY (id) LABEL v PROPERTIES (id, s));
ALTER TABLE t ALTER COLUMN s SET EXPRESSION AS (a * b);
ERROR: unexpected object depending on column: property s of label v
of vertex t of property graph g

Cause:
CREATE PROPERTY GRAPH records per-column dependencies (element keys via
array_of_attnums_to_objectaddrs, property expressions via
recordDependencyOnSingleRelExpr), but RememberAllDependentForRebuilding() in
tablecmds.c has no cases for PropgraphElementRelationId /
PropgraphLabelPropertyRelationId, so they reach the default: elog.
Still present in master as of dde9a87d4d0.

Expected, following the existing pattern in that switch:
- AT_AlterColumnType: user-facing ERRCODE_FEATURE_NOT_SUPPORTED error.
- AT_SetExpression: no error — column attnum and type are unchanged, so
there is nothing to rebuild.