nimiq-primitives: Panic in TrieProof::verify via child_index unwrap on equal-length keys

Impact A malicious peer acting as a state-sync source can crash a syncing node by sending a crafted TrieChunk whose proof contains two TrieProofNodes with identical keys. TrieProof::verify calls TrieProofNode::childindex primitives/src/trie/trieproofnode.rs:94, which unconditionally unwraps...