Cleanup some minor things

[lilizoey]

• Add VariantConversionError::VariantIsNil
• Implement Display and Error for VariantConversionError
• Remove Deref impl for Object with target () (this can cause weird things like being able to clone a Gd<Object> and get back a ())
• Add an #[allow] for a clippy lint that was added in 1.72

[GodotRust]

API docs are being generated and will be shortly available at: https://godot-rust.github.io/docs/gdext/pr-389

[Bromeon]

Thanks a lot! There seems to be a new clippy issue, other than that looks good 🙂

[lilizoey]

Thanks a lot! There seems to be a new clippy issue, other than that looks good 🙂

apparently ./check.sh clippy runs with no-default-features and not all-targets unlike the CI which seems to make that clippy lint not get triggered.

[Bromeon]

Thanks! I'll fix the local check.sh during my next PR.

[Bromeon]

Thanks! I'll fix the local check.sh during my next PR.

Actually, I noticed this was done deliberately, because changing features means we have to recompile everything. And for itest, we don't want to run with the full codegen locally.

So I don't think there's that much we can do; hopefully we can one day improve compile times to the point where codegen-full will no longer be necessary 😕