pgsql: Split contrib/cube platform-depended checks into separate test

Split contrib/cube platform-depended checks into separate test

We're currently maintaining two outputs for cube regression test. But that
appears to be unsuitable, because these outputs are different in out few checks
involving scientific notation. So, split checks involving scientific notation
into separate test, making contrib/cube easier to maintain. Backpatch to all
supported versions in order to make further backpatching easier.

Discussion: https://postgr.es/m/CAPpHfdvJgWjxHsJTtT%2Bo1tz3OR8EFHcLQjhp-d3%2BUcmJLh-fQA%40mail.gmail.com
Author: Alexander Korotkov
Backpatch-through: 9.3

Branch
------
REL9_5_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/26cbd23259403b27641d6c5a2798052aa3854e01

Modified Files
--------------
contrib/cube/Makefile | 2 +-
contrib/cube/expected/cube.out | 102 ---
contrib/cube/expected/cube_1.out | 1409 ----------------------------------
contrib/cube/expected/cube_2.out | 1409 ----------------------------------
contrib/cube/expected/cube_3.out | 1409 ----------------------------------
contrib/cube/expected/cube_sci.out | 106 +++
contrib/cube/expected/cube_sci_1.out | 106 +++
contrib/cube/expected/cube_sci_2.out | 106 +++
contrib/cube/expected/cube_sci_3.out | 106 +++
contrib/cube/sql/cube.sql | 17 -
contrib/cube/sql/cube_sci.sql | 22 +
11 files changed, 447 insertions(+), 4347 deletions(-)