[Cashtab] [p5 normalizeBalance fix] Improve name of normalizeBalance function

Summary:
T2601

Depends on D11846

Change name of normalizeBalance to getWalletBalanceFromUtxos

This is much more clear about what the function is actually doing. Not sure wtf I was thinking with the original normalize name.

Test Plan:
npm test

Note that this function is still only being referenced by the loadStoredWallet in cashMethods.js.

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D11847