hybrid-array: re-add AsRef<[T; N]>/AsMut<[T; N]> impls (#1031)

These were removed in #1026 for more consistency with core arrays.

However, `generic-array` provides these impls, which makes removing them
problematic when migrating `generic-array`-based code, so it's easier to
keep them around, even if it breaks inference due to overlapping impls.

Author: tarcieri

hybrid-array/src/lib.rs

@@ -212,6 +212,17 @@ where
     }
 }
 
+impl<T, U, const N: usize> AsRef<[T; N]> for Array<T, U>
+where
+    Self: ArrayOps<T, N>,
+    U: ArraySize,
+{
+    #[inline]
+    fn as_ref(&self) -> &[T; N] {
+        self.as_core_array()
+    }
+}
+
 impl<T, U> AsMut<[T]> for Array<T, U>
 where
     U: ArraySize,
@@ -222,6 +233,17 @@ where
     }
 }
 
+impl<T, U, const N: usize> AsMut<[T; N]> for Array<T, U>
+where
+    Self: ArrayOps<T, N>,
+    U: ArraySize,
+{
+    #[inline]
+    fn as_mut(&mut self) -> &mut [T; N] {
+        self.as_mut_core_array()
+    }
+}
+
 impl<T, U> Borrow<[T]> for Array<T, U>
 where
     U: ArraySize,