NodeCodec partials should just be impl Iterator<Item=u8>

[gnunicorn]

Needs refactoring here

substrate/core/trie/src/node_codec.rs

Lines 98 to 99 in bbe1816

	// FIXME: refactor this so that `partial` isn't already encoded with HPE. Should just be an `impl Iterator<Item=u8>`.
	fn leaf_node(partial: &[u8], value: &[u8]) -> Vec<u8> {

and here

substrate/core/trie/src/node_codec.rs

Lines 105 to 106 in bbe1816

	// FIXME: refactor this so that `partial` isn't already encoded with HPE. Should just be an `impl Iterator<Item=u8>`.
	fn ext_node(partial: &[u8], child: ChildReference<H::Out>) -> Vec<u8> {