pgsql: Add test case for same-type reordered FK columns

Add test case for same-type reordered FK columns

The test added in 980c1a85d819 covered reordered FK columns with
different types, which triggered an "operator not a member of opfamily"
error in the fast-path prior to that commit. Add a test for the
same-type case, which is also fixed by that commit but where the wrong
scan key ordering instead produced a spurious FK violation without any
internal error.

Reported-by: Fredrik Widlert <fredrik(dot)widlert(at)digpro(dot)se>
Discussion: https://postgr.es/m/CADfhSr8hYc-4Cz7vfXH_oV-Jq81pyK9W4phLrOGspovsg2W7Kw@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/009ea1b08d7b8843435bd0f1137fa3df09aac79f

Modified Files
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src/test/regress/expected/foreign_key.out | 10 ++++++++++
src/test/regress/sql/foreign_key.sql | 9 +++++++++
2 files changed, 19 insertions(+)