fix(driver-podman): compile container spec on macOS

[elezar]

Summary

Fix the macOS Podman driver compilation failure and extend the existing macOS Clippy guard to cover portable non-VM driver crates. This prevents the same cfg regression from reaching a release build.

Related Issue

No issue required: localized CI coverage maintenance and an obvious compilation fix following a release-build regression.

Regression links:

• Original release build: Build Gateway Binary (macOS)
• First PR commit only: Rust lint (macOS)

Changes

• Import Path unconditionally because it appears in an unconditional Podman container-spec function signature.
• Add the db-credstore, Docker, Kubernetes, Kubernetes Secrets, Podman, and Vault driver crates to macOS Clippy.
• Keep the VM driver excluded because its build script embeds runtime assets.

Testing

• mise run pre-commit passes (not run: mise and cargo are unavailable in this shell)
• Unit tests added/updated (not run: cargo is unavailable in this shell)
• Actions workflow YAML parses successfully
• git diff --check passes
• E2E tests added/updated (not applicable)

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)