[FIX] pg: avoid dropping not null constraints in pg18

In PG18 not null constraint names follow the '{table}_{column}_not_null' pattern
as opposed to the '[0-9_]+_not_null' one followed until pg17.

Our utils must be adapted to cope with that, otherwise the util will attempt to
drop not null constraints - failing against those of primary keys.

The following traceback is achieved when trying to upgrade a new demo db in PG18
with `mrp` installed, from 17.0 to 18.0:

```
2025-11-04 10:23:38,126 28873 ERROR test_mrp_17_18.0 odoo.sql_db: bad query: b'ALTER TABLE "mail_push" DROP CONSTRAINT IF EXISTS "mail_notification_web_push_id_not_null" '
ERROR: column "id" is in a primary key

2025-11-04 10:23:38,127 28873 WARNING test_mrp_17_18.0 odoo.modules.loading: Transient module states were reset
2025-11-04 10:23:38,129 28873 ERROR test_mrp_17_18.0 odoo.modules.registry: Failed to load registry
2025-11-04 10:23:38,129 28873 CRITICAL test_mrp_17_18.0 odoo.service.server: Failed to initialize database `test_mrp_17_18.0`.
Traceback (most recent call last):
  File "/home/odoo/src/odoo/18.0/odoo/service/server.py", line 1366, in preload_registries
    registry = Registry.new(dbname, update_module=update_module)
  File "<decorator-gen-13>", line 2, in new
  File "/home/odoo/src/odoo/18.0/odoo/tools/func.py", line 97, in locked
    return func(inst, *args, **kwargs)
  File "/home/odoo/src/odoo/18.0/odoo/modules/registry.py", line 129, in new
    odoo.modules.load_modules(registry, force_demo, status, update_module)
  File "/home/odoo/src/odoo/18.0/odoo/modules/loading.py", line 485, in load_modules
    processed_modules += load_marked_modules(env, graph,
  File "/home/odoo/src/odoo/18.0/odoo/modules/loading.py", line 365, in load_marked_modules
    loaded, processed = load_module_graph(
  File "/home/odoo/src/odoo/18.0/odoo/modules/loading.py", line 182, in load_module_graph
    migrations.migrate_module(package, 'pre')
  File "/home/odoo/src/odoo/18.0/odoo/modules/migration.py", line 222, in migrate_module
    exec_script(self.cr, installed_version, pyfile, pkg.name, stage, stageformat[stage] % version)
  File "/home/odoo/src/odoo/18.0/odoo/modules/migration.py", line 259, in exec_script
    mod.migrate(cr, installed_version)
  File "/home/odoo/src/upgrade/migrations/mail/saas~17.1.1.16/pre-migrate.py", line 30, in migrate
    util.rename_model(cr, "mail.notification.web.push", "mail.push")
  File "/home/odoo/src/upgrade-util/src/util/models.py", line 308, in rename_model
    pg_rename_table(cr, old_table, new_table)
  File "/home/odoo/src/upgrade-util/src/util/pg.py", line 1354, in rename_table
    remove_constraint(cr, new_table, const, warn=False)
  File "/home/odoo/src/upgrade-util/src/util/pg.py", line 853, in remove_constraint
    cr.execute(format_query(cr, "ALTER TABLE {} DROP CONSTRAINT IF EXISTS {} {}", table, name, cascade))
  File "/home/odoo/src/odoo/18.0/odoo/sql_db.py", line 357, in execute
    res = self._obj.execute(query, params)
psycopg2.errors.InvalidTableDefinition: column "id" is in a primary key
```

Author: Pirols

src/util/pg.py

@@ -1333,14 +1333,14 @@ def rename_table(cr, old_table, new_table, remove_constraints=True):
         )
 
     if remove_constraints:
-        # DELETE all constraints, except Primary/Foreign keys, they will be re-created by the ORM
-        # NOTE: Custom constraints will instead be lost
+        # DELETE all constraints, except Primary/Foreign keys/not null checks, they will be re-created by the ORM
+        # NOTE: Custom constraints will instead be lost, except for not null ones
         cr.execute(
-            """
+            r"""
             SELECT constraint_name
               FROM information_schema.table_constraints
              WHERE table_name = %s
-               AND constraint_name !~ '^[0-9_]+_not_null$'
+               AND constraint_name !~ '^\w+_not_null$'
                AND (  constraint_type NOT IN ('PRIMARY KEY', 'FOREIGN KEY')
                    -- For long table names the constraint name is shortened by PG to fit 63 chars, in such cases
                    -- it's better to drop the constraint, even if it's a foreign key, and let the ORM re-create it.
@@ -1353,24 +1353,29 @@ def rename_table(cr, old_table, new_table, remove_constraints=True):
             _logger.info("Dropping constraint %s on table %s", const, new_table)
             remove_constraint(cr, new_table, const, warn=False)
 
-    # rename fkeys
+    # rename constraints
     cr.execute(
         """
         SELECT constraint_name
           FROM information_schema.table_constraints
          WHERE table_name = %s
-           AND constraint_type = 'FOREIGN KEY'
-           AND constraint_name LIKE %s
+           AND (
+               constraint_name ~ %s
+               OR (
+                   constraint_type = 'FOREIGN KEY'
+                   AND constraint_name LIKE %s
+                  )
+               )
         """,
-        [new_table, old_table.replace("_", r"\_") + r"\_%"],
+        [new_table, "^" + re.escape(old_table) + r"_\w+_not_null$", old_table.replace("_", r"\_") + r"\_%"],
     )
     old_table_length = len(old_table)
-    for (old_fkey,) in cr.fetchall():
-        new_fkey = new_table + old_fkey[old_table_length:]
-        _logger.info("Renaming FK %r to %r", old_fkey, new_fkey)
+    for (old_const,) in cr.fetchall():
+        new_const = new_table + old_const[old_table_length:]
+        _logger.info("Renaming constraint %r to %r", old_const, new_const)
         cr.execute(
             sql.SQL("ALTER TABLE {} RENAME CONSTRAINT {} TO {}").format(
-                sql.Identifier(new_table), sql.Identifier(old_fkey), sql.Identifier(new_fkey)
+                sql.Identifier(new_table), sql.Identifier(old_const), sql.Identifier(new_const)
             )
         )