Upgrade to Rust 1.78

[maspe36]

We are currently on Rust 1.74, and now as of Rust 1.78, the u128 type is now FFI safe. Lets go ahead and upgrade.

Doing this upgrade will help us resolve #320 once and for all. As part of this upgrade, we should also remove the #![allow(improper_ctypes)] and #![allow(improper_ctypes_definitions)] lines from our rcl bindings as we no longer need to ignore these lints.

[Guelakais]

I'm currently working on. Is there a reason why you have set the rust version in cargo.toml for rclrs?

[maspe36]

That rust version is supposed to be the minimum supported version of rust that rclrs would work with. However, our CI does not use this same version so there is a chance that its actually misleading now.

I think with this upgrade to at least Rust 1.78 we'd want to upgrade rclrs to 1.78 in the cargo.toml as well since we would depend on u128 FFI safe functions.