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.widlert@digpro.se>
Discussion: https://postgr.es/m/CADfhSr8hYc-4Cz7vfXH_oV-Jq81pyK9W4phLrOGspovsg2W7Kw@mail.gmail.com