Fix Windows binary builds and publish job artifact download failure

• Expanded PHP versions in test matrix to include 8.1 (minimum supported version) and 8.2 everywhere

win32-x64 / win32-arm64 — wrong library names in spc download

Root cause: SPC_WINDOWS_LIBS used bare names postgresql and libiconv,
which download the Unix source tarballs and register download locks under those
names. SPC's Windows build system then looks for postgresql-win and
libiconv-win (pre-built Visual C++ binary packages), finds no lock entry, and
fails immediately:

Building required lib [postgresql-win]
Source [postgresql-win] not downloaded or not locked, you should download it first!

Fix: Use the correct Windows package names in SPC_WINDOWS_LIBS:

# Before
libiconv,libxml2,postgresql,sqlite

# After — explicit -win suffix for the VC++ prebuilt packages
libiconv-win,libxml2,postgresql-win,sqlite

libxml2 and sqlite are built from source on all platforms and have no -win variant.

Publish job — Docker build-cache artifacts crash the download step

Root cause: The download-artifact step had no pattern filter, so it
attempted to download every artifact in the run — including
DBDiff~DBDiff~*.dockerbuild build-cache blobs uploaded by the Docker job.
Those are internal BuildKit cache references that cannot be downloaded as normal
artifacts, causing:

Unable to download artifact(s): Unable to download and extract artifact:
Artifact download failed after 5 retries.

This killed the entire publish job even when all required dbdiff-* artifacts
were available.

Fix: Add pattern: dbdiff-* to the download-artifact step so only PHAR
and binary artifacts are fetched:

- uses: actions/download-artifact@v4
  with:
    path: binaries/
    pattern: dbdiff-*
    merge-multiple: false