Improve test output of extended statistics for ndistinct and dependencies

Improve test output of extended statistics for ndistinct and dependencies

Corey Huinker has come up with a recipe that is more compact and more
pleasant to the eye for extended stats because we know that all of them
are 1-dimension JSON arrays.  This commit switches the extended stats
tests to use replace() instead of jsonb_pretty(), splitting the data so
as one line is used for each item in the extended stats object.

This results in the removal of a good chunk of test output, that is now
easier to debug with one line used for each item in a stats object.
This patch has not been provided by Corey.  This is some post-commit
cleanup work that I have noticed as good enough to do on its own while
reviewing the rest of the patch set Corey has posted.

Discussion: https://postgr.es/m/CADkLM=csMd52i39Ye8-PUUHyzBb3546eSCUTh-FBQ7bzT2uZ4Q@mail.gmail.com