Fix Unknown method: SetInteractive for agama questions mode non-interactive (#709)

[mvidner]

Problem

See #709:

When I use our CLI, agama questions mode non-interactive
It calls a org.opensuse.Agama.Questions1.SetInteractive method on /org/opensuse/Agama/Questions1 but the actual API is an Interactive property.

Solution

Fix the generated proxies to include a dbus_proxy(property) attribute.

(other proxies.rs files either do not have writable properties or already have this fix applied)

An upstream fix for https://github.com/dbus2/zbus will follow.

Testing

Tested manually:

567764a093c4:/checkout # rust/target/debug/agama questions mode non-interactive
Failed to set mode for answering questions.

Caused by:
    org.freedesktop.DBus.Error.UnknownMethod: Unknown method 'SetInteractive'
567764a093c4:/checkout # [apply this fix]
567764a093c4:/checkout # (cd rust; cargo b)
   Compiling agama-lib v1.0.0 (/checkout/rust/agama-lib)
   Compiling agama-cli v1.0.0 (/checkout/rust/agama-cli)
   Compiling agama-dbus-server v0.1.0 (/checkout/rust/agama-dbus-server)
    Finished dev [unoptimized + debuginfo] target(s) in 13.53s
567764a093c4:/checkout # rust/target/debug/agama questions mode non-interactive
11:47:52 [INFO] interactive value unchanged - false

Screenshots

See above.

[mvidner]

The NetworkManager proxies fixed here are not used in our client code. I checked with rg -F .set_ rust/ and eyeball-diffed the resulting agama-lib/src/network/ matches.