Cache MinIO binary for Windows CI

[LOCEANlloydizard]

#1784 fixed the MinIO download issue for Windows CI but while fixing this, we realized that the MinIO binary (~108 MB) is downloaded separately for each Windows integration matrix job. We need to optimize this, possibly by caching .ci_helpers/minio.exe with GitHub Actions, using the pinned MinIO release/version as part of the cache key, to avoid unnecessary repeated downloads (and reduce CI time)

[LOCEANlloydizard]

Closing as superseded by #1798 which removes MinIO from the test infrastructure and replaces it with SeaweedFS, so the proposed MinIO caching is no longer needed!