[Feature] Apply zero traces to a SMT trie

[cffls]

Create a function that, given a list of zero traces and an initial SMT state, it applies the traces on top of the initial state trie, and returns a new trie.

Implementation

A zero trace contains a list of changes a transaction will make to the trie state.

• Implement StateWriter in SMT. Notice that StateReader interface is already implemented.
• Use the functions exposed by StateWriter to mutate the state trie.

The interface of the function should look something like this:

func ApplyTraces(s *SMT, traces []TxnTrace) (*SMT, error) {
    // Implementation will go here
}