fix(ironfish): Fix unlock hanging in memory client CLI

[rohanjadvani]

Summary

When unlocking a wallet without a running node (i.e. using the rpc memory client), the process will hang until the timeout to re-lock the wallet is called (by default, this is 24h). There are several ways to address this issue:

• Don't enqueue a timeout if unlocking via the UI utility in the CLI. This is not ideal, because if you have a running node, you may just leave it unlocked indefinitely. We can add further logic to prevent this probably.
• Remove the utility to unlock the wallet, but that ruins UX a bit.

This PR does several things:

• Implement the close method for the memory client. This did nothing before, but now shuts down the node connection
• Destroy the master key and clear any timeouts before checking if the wallet is started.

Testing Plan

Run CLI commands

Documentation

Does this change require any updates to the Iron Fish Docs (ex. the RPC API
Reference)? If yes, link a
related documentation pull request for the website.

[ ] Yes

Breaking Change

Is this a breaking change? If yes, add notes below on why this is breaking and label it with breaking-change-rpc or breaking-change-sdk.

[ ] Yes