feat(kv_typed): impl AsBytes for all SmallVec (use const generics)

tools/kv_typed/src/as_bytes.rs

@@ -26,20 +26,16 @@ where
     }
 }
 
-macro_rules! impl_as_bytes_for_smallvec {
-    ($($N:literal),*) => {$(
-        impl<T> AsBytes for SmallVec<[T; $N]>
+impl<T, const N: usize> AsBytes for SmallVec<[T; N]>
 where
     T: zerocopy::AsBytes,
+    [T; N]: smallvec::Array<Item = T>,
 {
     fn as_bytes<D, F: FnMut(&[u8]) -> D>(&self, mut f: F) -> D {
         use zerocopy::AsBytes as _;
         f((&self[..]).as_bytes())
     }
 }
-    )*};
-}
-impl_as_bytes_for_smallvec!(1, 2, 4, 8, 16, 32, 64);
 
 impl<T> AsBytes for BTreeSet<T>
 where