simplify iterator state constructor arguments

Signed-off-by: Jason Volk <jason@zemos.net>

src/database/map/keys_from.rs

@@ -54,7 +54,7 @@ where
 	use crate::pool::Seek;
 
 	let opts = super::iter_options_default();
-	let state = stream::State::new(&self.db, &self.cf, opts);
+	let state = stream::State::new(self, opts);
 	if is_cached(self, from) {
 		return stream::Keys::<'_>::from(state.init_fwd(from.as_ref().into())).boxed();
 	}