zvariant-5.15.0

CI

• 💚 Work around nightly rustfmt macro mangling.

Deprecated

• 🗑️ Deprecate GVariant support in zvariant.

Documentation

• 📝 Point GVariant users to the zgvariant crate.

Fixed

• 🐛 Support zvariant_utils/gvariant being enabled externally. #1910

Removed

• 🔥 Remove the gvariant fuzz target.
• 🔥 Remove gvariant benches, ostree tests and test data.