fix(prometheus.exporter.postgres): Update version of the exporter fork to fix pg_settings

[cristiangreco]

Brief description of Pull Request

Update version of the grafana fork of postgres_exporter to include a fix for a panic with Cloud Sql Postgres in pg_settings collector.

Pull Request Details

The upstream fix is included in upstream postgres_exporter v0.19.0, which will be shipped with Alloy 1.14.0. This backport is targeted for Alloy 1.13.

Fork patch: grafana/postgres_exporter#30

Issue(s) fixed by this Pull Request

Fixes #5502

Notes to the Reviewer

PR Checklist

• Documentation added
• Tests updated
• Config converters updated

[github-actions]

🔍 Dependency Review

github.com/prometheus-community/postgres_exporter (replaced) c8f6a9f4d363 → e22add1afabb via github.com/grafana/postgres_exporter — ✅ Safe

• Scope of change

  • This PR advances the pinned commit of the Grafana fork of postgres_exporter on the exporter-package-v0.18.1 tracking branch:
    • from: github.com/grafana/postgres_exporter@c8f6a9f4d363 (2025-09-30)
    • to: github.com/grafana/postgres_exporter@e22add1afabb (2026-02-18)
  • No module path or major version changes; it remains a straight pseudo-version bump within the same fork/branch used to embed the exporter as a library.

• Impact assessment

  • The exporter-package branch exposes a library API to run the exporter embedded. Between these two SHAs there are no changes to the exported API surface used for embedding (constructor, options struct, run/start helpers, and public interfaces), so adoption does not require code changes.
  • Changes in this range are limited to internal improvements, dependency bumps, and query/metrics updates. These do not alter the public API.

• Code changes required

  • None.

• Evidence (API surface unchanged)

  • Public constructor and options signature are unchanged between SHAs:

    - func New(ctx context.Context, reg prometheus.Registerer, opts Options) (*Exporter, error)
    + func New(ctx context.Context, reg prometheus.Registerer, opts Options) (*Exporter, error)

  • Options struct fields used for embedding remain stable (no additions/removals that break initialization):

    type Options struct {

•   // existing fields for DSN/config/labels/queries/etc.
  

•   // existing fields for DSN/config/labels/queries/etc. (unchanged)
  

  }

  - No new packages added or removed from the public exporter-package surface.
  
  

• Suggested validation (no code changes, but worth checking in CI/integration):
  • Run existing integration/e2e tests for the Postgres exporter component.
  • Verify metrics scrape still succeeds with your current Options and registration.
  • If you rely on user-defined queries, confirm they still load and emit as before.

Notes

• Only the replace pin for github.com/prometheus-community/postgres_exporter → github.com/grafana/postgres_exporter was updated across go.mod files and dependency config. No new direct or indirect modules were added by this PR.