Revert "Fix psql's single transaction mode on client-side errors with -c/-f switches".

Revert "Fix psql's single transaction mode on client-side errors with -c/-f switches".

This reverts commits a04ccf6df et al. in the back branches only.
There was some disagreement already over whether to back-patch
157f8739a, on the grounds that it is the sort of behavioral
change that we don't like to back-patch.  Furthermore, it now
looks like the logic needs some more work, which we don't have
time for before the upcoming 14.4 release.  Revert for now, and
perhaps reconsider later.

Discussion: https://postgr.es/m/17504-76b68018e130415e@postgresql.org