[codex] add credcheck extension overlay

[4mGLn]

Issue

The portable PostgreSQL release pipeline did not publish an overlay for the upstream credcheck extension, leaving credential policy support out of the generated third-party extension artifacts.

Cause and effect

External extensions are selected from ci/postgresql-release-config.json. Because credcheck was absent from separate_extensions, the existing overlay build loop never cloned, compiled, or packaged it for any PostgreSQL release or target.

Fix

Added HexaCluster/credcheck to the separate extension configuration and pinned it to the released v5.0 tag. The existing CI pipeline will now build and publish matching Linux and Windows overlay archives for PostgreSQL 16, 17, and 18. The generated overlay README includes the shared_preload_libraries requirement and CREATE EXTENSION credcheck; command.

The top-level README now lists credcheck among the available third-party overlays.

Validation

• jq empty ci/postgresql-release-config.json
• bash -n scripts/ci/*.sh scripts/run_local_build.sh
• git diff --check

[chatgpt-codex-connector]

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