[Cashtab] Compare latest utxo set to stored wallet state

Summary:
If wallet has utxo set in state, then the utxosHaveChanged check should be performed against wallet.state and not previousUtxos

Issue: If user activates a new wallet from their saved wallets, utxosChanged will always be true if the app is checking previousUtxos instead of the previous utxo state of the loaded wallet.

After more local testing, turns out the issue described in D9516 was not happening in general, but only in a specific case being tested locally. So, this diff restores the original functionality, while keeping the cleaned up syntax of D9516.

Test Plan: npm test

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D9521