pgsql: Re-add BRIN isolation test

Re-add BRIN isolation test

This time, instead of using a core isolation test, put it on its own
test module; this way it can require the pageinspect module to be
present before running.

The module's Makefile is loosely modeled after test_decoding's, so that
it's easy to add further tests for either pg_regress or isolationtester
later.

Backpatch to 9.5.

Branch
------
master

Details
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http://git.postgresql.org/pg/commitdiff/672e3ec0e93e3d2d5549b95f73b2a3ab58714146

Modified Files
--------------
src/test/modules/Makefile                          |    1 +
src/test/modules/brin/.gitignore                   |    3 ++
src/test/modules/brin/Makefile                     |   30 +++++++++++++
.../summarization-and-inprogress-insertion.out     |   39 +++++++++++++++++
.../summarization-and-inprogress-insertion.spec    |   44 ++++++++++++++++++++
5 files changed, 117 insertions(+)