pgsql: Add a test harness for the binary heap code.

Add a test harness for the binary heap code.

binaryheap is heavily used and already has decent test coverage,
but it lacks dedicated tests for its correctness.  This commit
changes that.

Author: Aleksander Alekseev <aleksander@tigerdata.com>
Discussion: https://postgr.es/m/CAJ7c6TMwp%2Bmb8MMoi%3DSMVMso2hYecoVu2Pwf2EOkesq0MiSKxw%40mail.gmail.com

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/b597ae6cc128b17038d461c5aa426d42f9cc33f9

Modified Files
--------------
src/test/modules/Makefile                          |   1 +
src/test/modules/meson.build                       |   1 +
src/test/modules/test_binaryheap/.gitignore        |   4 +
src/test/modules/test_binaryheap/Makefile          |  24 ++
.../test_binaryheap/expected/test_binaryheap.out   |  12 +
src/test/modules/test_binaryheap/meson.build       |  33 +++
.../test_binaryheap/sql/test_binaryheap.sql        |   8 +
.../test_binaryheap/test_binaryheap--1.0.sql       |   7 +
src/test/modules/test_binaryheap/test_binaryheap.c | 275 +++++++++++++++++++++
.../test_binaryheap/test_binaryheap.control        |   5 +
10 files changed, 370 insertions(+)