pgsql: postgres_fdw: Split out the query_cancel test to its own file

postgres_fdw: Split out the query_cancel test to its own file

This allows us to skip it in Cygwin, where it's reportedly flaky because
of platform bugs or something.

Backpatch to 17, where the test was introduced by commit 2466d6654f85.

Reported-by: Alexander Lakhin <exclusion(at)gmail(dot)com>
Discussion: https://postgr.es/m/e4d0cb33-6be5-e4d5-ae49-9eac3ff2b005@gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/90c1ba52e06d0847e524b6e6c3259ab1843bb05f

Modified Files
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contrib/postgres_fdw/Makefile | 2 +-
contrib/postgres_fdw/expected/postgres_fdw.out | 16 ----------------
contrib/postgres_fdw/expected/query_cancel.out | 20 ++++++++++++++++++++
contrib/postgres_fdw/expected/query_cancel_1.out | 3 +++
contrib/postgres_fdw/meson.build | 1 +
contrib/postgres_fdw/sql/postgres_fdw.sql | 8 --------
contrib/postgres_fdw/sql/query_cancel.sql | 12 ++++++++++++
7 files changed, 37 insertions(+), 25 deletions(-)