Generate glib::object::Object::new instead of unsafe code

[msrd0]

This removes all unsafe code that was previously being generated by the proc macro. Also simplifies the code a bit.

[antoyo]

Thanks for your contribution!

The CI now fails with some clippy warnings.

Can you please add the following at the crate root to silence those warnings?

#![allow(clippy::uninlined-format-args)]

[msrd0]

Should be fixed now

[antoyo]

I guess you'll need to add allow(unknown_lints) as well since it seems the clippy lint is not on stable yet.

[msrd0]

It looks like that didn't help. Maybe it would be sufficient to run clippy only on one Rust version?

[antoyo]

It seems like unknown_lints should come before the unknown lint in the list.

[msrd0]

Interesting, I didn't know the order had any effect

[antoyo]

Thanks!