pgsql: Test passing expanded-value representations to workers.

Test passing expanded-value representations to workers.

Currently, we don't have an explicit test to pass expanded-value
representations to workers, so we don't know whether it works on all kind
of platforms.  We suspect that the current code won't work on
alignment-sensitive hardware.  This commit will test that aspect and can
lead to failure on some of the buildfarm machines which we will fix in the
later commit.

Author: Tom Lane and Amit Kapila
Discussion: https://postgr.es/m/11629.1536550032@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/0fd6a8a7d0ce6dcf0edb8330fe7e6d6fde8f40db

Modified Files
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src/test/regress/expected/select_parallel.out | 29 ++++++++++++++++++++++++++-
src/test/regress/sql/select_parallel.sql      | 18 ++++++++++++++++-
2 files changed, 45 insertions(+), 2 deletions(-)