The main ExplainAnalyzeTestCase tests in here were running standard
TPC-H-like test queries, and checking that the EXPLAIN ANALYZE output
contains a "Memory: " line for every plan node. That seems a bit excessive,
because looking at how those lines are printed, there is no reason to
believe that you might have a Memory line for some nodes but not others.
I don't think we need to test for that.

In order to still have minimal coverage for the explain_memory_verbosity
GUC, add a small test case to the main regression suite for that.

The mpp20785 test was testing for an old bug where you got an out of
memory error with this query. However, the test was broken, because the
test schema was nowhere to be found, so it simply resulted in a "schema not
found" error. Perhaps we could put it back if we could find the original
schema somewhere, but it's useless as it is.