Fix psql's ON_ERROR_ROLLBACK so that it handles COMMIT AND CHAIN.

 Fix psql's ON_ERROR_ROLLBACK so that it handles COMMIT AND CHAIN.
 
 When ON_ERROR_ROLLBACK is enabled, psql releases a temporary savepoint
 if it's idle in a valid transaction block after executing a query. But psql
 doesn't do that after RELEASE or ROLLBACK is executed because a temporary
 savepoint has already been destroyed in that case.
 
 This commit changes psql's ON_ERROR_ROLLBACK so that it doesn't release
 a temporary savepoint also when COMMIT AND CHAIN is executed. A temporary
 savepoint doesn't need to be released in that case because
 COMMIT AND CHAIN also destroys any savepoints defined within the transaction
 to commit. Otherwise psql tries to release the savepoint that
 COMMIT AND CHAIN has already destroyed and cause an error
 "ERROR:  savepoint "pg_psql_temporary_savepoint" does not exist".
 
 Back-patch to v12 where transaction chaining was added.
 
 Reported-by: Arthur Nascimento
 Author: Arthur Nascimento
 Reviewed-by: Fujii Masao, Vik Fearing
 Discussion: https://postgr.es/m/16867-3475744069228158@postgresql.org