Allow rename of container with &'static str

[DanielBauman88]

Since the last issue #450 was closed there seems to have been a fair bit of interest.
The last two comments referring to implementing this functionality have 4 and 11 "+1"s.

Additionally, it seems like this would now be doable without needing a new attribute like rename_const.

In light of this now being supported, I think this is worth re-opening.

[Victor-N-Suadicani]

I just ran into this as I tried doing something like this:

trait FieldName {
    const FIELD_NAME: &'static str;
}

#[derive(Serialize, Deserialize)]
struct MyStruct<T: FieldName> {
    #[serde(rename = T::FIELD_NAME)]
    renamed_field: i32,
}

I honestly just assumed this would work but unfortunately it doesn't 😞.