refactor: simplify trie_walker get_proof code

[KolbyML]

What was wrong?

the reverse logic for path was a little overly complex

How was it fixed?

by making the logic less complex

[morph-dev]

How about using VecDeque. Something like this:

pub fn get_proof(&self, node_hash: B256) -> TrieProof {
    let mut path_parts = VecDeque::new();
    let mut proof = VecDeque::new();
    let mut next_node: Option<B256> = Some(node_hash);
    while let Some(current_node) = next_node {
        let Some(node) = self.nodes.get(&current_node) else {
            panic!("Node not found in trie walker nodes. This should never happen.");
        };
        path_parts.push_front(node.path_nibbles.clone());
        proof.push_front(node.encoded_node.clone().into());
        next_node = node.parent_hash;
    }

    TrieProof {
        path: Vec::from(path_parts).concat(),
        proof: Vec::from(proof),
    }
}

In my opinion, it's easier to follow logic without tracking what is reversed and what not. It's up to you (i'm fine with merging as is as well).