Change the test from using the old x_diff method to the new
direct diff method for checking that the results don't differ
in the optimized and unoptimized cases. This cleans up the
golden file so that in case of success the golden files are
nearly empty instead of containing a diff file that must
be checked to ensure that it only has explain (and not tuple)
output. Also combine several test files into query.sql, and
get rid of differences in pg versions.
