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