Add TryFrom for PartialDuration to Duration (#585)

This PR adds a `TryFrom` implemenation for converting a PartialDuration
to Duration.

The core reasoning is to simplify the case where someone would want to
add a single day in Rust.

```rust
use temporal_rs::{Temporal, PlainDate, partial::PartialDuration};

let today = Temporal::now().plain_date_iso(None).unwrap();
let one_day = PartialDuration::empty().with_days(1);
// Before: 
// let tomorrow = today.add(Duration::from_partial_duration(one_day).unwrap()).unwrap()
// After:
let tomorrow = today.add(one_day.try_into().unwrap()).unwrap();
```

Author: nekevss

src/builtins/core/duration.rs

@@ -333,6 +333,13 @@ impl core::fmt::Display for Duration {
     }
 }
 
+impl TryFrom<PartialDuration> for Duration {
+    type Error = TemporalError;
+    fn try_from(partial: PartialDuration) -> Result<Self, Self::Error> {
+        Duration::from_partial_duration(partial)
+    }
+}
+
 // NOTE(nekevss): Structure of the below is going to be a little convoluted,
 // but intended to section everything based on the below
 //