feat: images tests and release on pg 17 and orioledb for multigres

[samrose]

New files (2):

• Dockerfile-multigres-17 — near-identical copy of Dockerfile-17 with 4 changes (no docker-entrypoint.sh, no WAL-G scripts, tail -f /dev/null
  entrypoint, no pgBackRest)
• Dockerfile-multigres-orioledb-17 — same treatment for the OrioleDB variant

Modified files (4):

• .github/workflows/docker-image-test.yml — added multigres Dockerfiles to matrix, skip standard tests for them, added smoke test with
  --entrypoint "" override
• .github/workflows/dockerhub-release-matrix.yml — auto-discovers multigres Dockerfiles, derives -multigres tags from base variant versions
• .github/workflows/manual-docker-release.yml — same auto-discovery + tag derivation, plus preserves -multigres suffix when
  inputs.postgresVersion is set
• nix/packages/docker-image-inputs.nix — tracks the two new Dockerfiles in the fileset

Goal, create 2 images that multigres can use to integrate with supabase postgres, and orioledb postgres

[cuongdo]

https://github.com/supabase/postgres/actions/runs/22699135346/job/65812194561?pr=2054#step:6:1411

shows that pgbackrest 2.57.0 is being pulled in. Ideally, we'd use 2.58.0, but 2.57.0 is fine. The pgbackrest part specifically looks good to me. I'm not sure how to review the rest.

[mkindahl]

Thanks for working on this. I have some short questions below for your consideration.

[cuongdo]

I took another look at this, and this looks like a good starting point for pgctld and pgbackrest. We will have to test and iterate to get things completely right, because Multigres generates Postgres config files based on its own template. We will need to modify the Multigres code to use the Postgres config here as a starting point. This PR looks good from my point of view.

[mkindahl]

LGTM

[Crispy1975]

Intentionally disabled?