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(at)tigerdata(dot)com>
Discussion: https://postgr.es/m/CAJ7c6TMwp%2Bmb8MMoi%3DSMVMso2hYecoVu2Pwf2EOkesq0MiSKxw%40mail.gmail.com

Branch
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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(+)