Add fuse-conv-bn method for Conv2d (#1196)

* Add fuse-conv-bn method for Conv2d

* no unwrap

* run rustfmp and clippy

candle-nn/src/batch_norm.rs

@@ -109,6 +109,10 @@ impl BatchNorm {
         &self.running_var
     }
 
+    pub fn eps(&self) -> f64 {
+        self.eps
+    }
+
     pub fn weight_and_bias(&self) -> Option<(&Tensor, &Tensor)> {
         self.weight_and_bias.as_ref().map(|v| (&v.0, &v.1))
     }