Improve regression test coverage for psql output formats.

Improve regression test coverage for psql output formats.

As penance for the "\pset format latex" silliness, add some regression
test coverage for the off-the-beaten-path output formats, which formerly
had exactly no coverage, except for some poorly-thought-out (unreadable,
repetitive, and incomplete) tests for asciidoc format.

I make no claims for the behavior exposed here actually being correct;
these test cases are just designed to ensure full code coverage in
fe_utils/print.c.  This brings the line coverage for that file up
from ~60% to ~93%.