All components should implement From<InnerDatatype> in Rust backend

[teh-cmc]

Since we now treat components as merely a tag on top of a datatype, there is always a trivial conversion that exists between a component and its underlying datatype, namely:

impl From<InnerDatatype> for OuterComponent {
    pub fn from(inner: InnerDatatype) -> Self {
        Self(inner)
    }
}

Similarly, there doesn't seem to be any reason for a component not to be attr.rerun.tuple_struct at this point.