🔖 zvariant_utils 3.0.0

• 🧑‍💻 Add support for multiple lists to def_attrs! macro.
• ✨ Add Signature type that represents a D-Bus type signature in parsed form.
• 🚚 Move serialized::Format from zvariant to zvariant_utils.
• 🔥 Drop old_new macro. Also the related AttrParse trait. We only needed it to support the
  old dbus_proxy and dbus_interface attributes in zbus macros but we just dropped them.
• 🚩 Add gvariant cargo feature. This is the same feature flag we've in other crates.
• ➕ New deps:
  • serde
  • nom
  • static_assertions
• ⬆️ Bump MSRV to 1.81.