pgsql: injection_points: Add support and tests for runtime arguments

injection_points: Add support and tests for runtime arguments

This commit provides some test coverage for the runtime arguments of
injection points, for both INJECTION_POINT_CACHED() and
INJECTION_POINT(), as extended in 371f2db8b05e.

The SQL functions injection_points_cached() and injection_points_run()
are extended so as it is possible to pass an optional string value to
them.

Reviewed-by: Greg Burd <greg(at)burd(dot)me>
Discussion: https://postgr.es/m/Z_y9TtnXubvYAApS@paquier.xyz

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/36e5fda6326045f4523568d4c9d682ee5d2f0867

Modified Files
--------------
.../injection_points/expected/injection_points.out | 45 ++++++++++++++++++++++
.../injection_points/injection_points--1.0.sql | 10 +++--
.../modules/injection_points/injection_points.c | 38 +++++++++++++++---
.../injection_points/sql/injection_points.sql | 10 +++++
4 files changed, 93 insertions(+), 10 deletions(-)