Using LibPq in TAP tests via FFI

Over at [1] Andres expressed enthusiasm for enabling TAP tests to call
LibPQ directly via FFI, and there was some support from others as well.
Attached is a very rough POC for just that.There are two perl modules,
one which wraps libpq (or almost all of it) in perl, and another which
uses that module to create a session object that can be used to run SQL.
Also in the patch is a modification of one TAP test (arbitrarily chosen
as src/bin/pg_amcheck/t/004_verify_heapam.p) to use the new interface,
so it doesn't use psql at all.

There's a bunch of work to do here, but for a morning's work it's not
too bad :-) Luckily I had most of the first file already to hand.

Next I plan to look at some of the recovery tests and other uses of
background_psql, which might be more challenging,a dn require extension
of the session API. Also there's a lot of error checking and
documentation that need to be added.

cheers

andrew

[1]  https://postgr.es/m/20240612152812.ixz3eiz2p475gose@awork3.anarazel.de

--
Andrew Dunstan
EDB: https://www.enterprisedb.com