Separate quantized phi-3 implementation. (#2157)

* Separate quantized phi-3 implementation.

* Integrate the quantized phi3 model.=

* Small fixes, get the generation to work properly.

* Keep the old llama implementation around.

* Change the default.

candle-core/src/metal_backend/mod.rs

@@ -676,9 +676,6 @@ impl BackendStorage for MetalStorage {
             }
         }
 
-        if layout.is_contiguous() {
-        } else {
-        }
         Ok(Self::new(buffer, device.clone(), el_count, dtype))
     }