Fixes github issue #2195, reported by @Toknowledge.

In the updated tests, we used functions like disable_xform and
enable_xform to hint the optimizer to disallow/allow a particular
physical node. However, these functions are only available when GPDB
is built with GPORCA. Planner on the other hand accomplished this
via a GUC.

To avoid usage of these functions in tests, I have introduced couple
of GUCS that mimic the same planner behavior but now for GPORCA.
In this effort I needed to add an API inside GPORCA.

When we create Left Anti Semi Join relations in case the left
side is a dummy relation, it implies that the join relation
is also a dummy relation.
Signed-off-by: NOmer Arap <oarap@pivotal.io>

When the size of the inner tuple in a MergeJoin is large, planner
decides to place a Materialize on the top of the inner Sort operator.
Furthemore if there is any Motion below the MergeJoin,
mjnode->prefetch_inner is set to true.

During execution of plan that has a Motion underneath a Materialize
underneath a MJ, MJ retrieves one tuple from the Motion (via
Materialize) and then resets the stream (by calling ExecReScan). Since
the Materialize underneath is initialized with incorrect eflags, it
deletes its tuplestore, instead of rewinding its cursor.  This fix sets
the right eflags value during Init (see comments in ExecMaterialReScan).

We explicitly checked if the subplan was projection-capable, and added
the hash expression ot the subplan's target list if it was. But projecting
the hash expression is not optional, you get a crash if you don't do it. So
instead of doing it only when the subplan is projection-capable, insert a
Result node if needed.

Forgot to update this in previous commit, when I added a test query to the
test.

pg_regress uses a tool called gpdiff.pl in order to compare diffs between
expected and actual result files in installcheck-good. pg_regress was hard
coded to always invoke gpdiff.pl to ignore NOTICE statements. Instead it would
be better to selectively ignore some NOTICE statements which are harmless and
which show up very often and compare the rest. This patch causes pg_regress to
invoke gpdiff.pl with an init_file which contains patterns that are to be
ignored.