uniffi should pass sequence arguments as slices

[eoger]

Right now uniffi will call Rust using owned vectors, which isn't super idiomatic, we should special case this and pass &[T] instead.

┆Issue is synchronized with this Jira Task ┆Issue Number: UNIFFI-14

[linabutler]

That sounds great! We could always add an Owned or ByVal (to match ByRef) annotation or something if a Rust function needs to take ownership of the sequence and calling .clone() is too expensive. But &[T] sounds perfect for the default.

[conanoc]

Any progress on this?

[badboy]

[ByRef] sequence<T> in argument position in the UDL works as expected.