Introduce new function `getBalanceSats` which gets the total balance in satoshis from an array of chronik utxos
This is part of a broader effort to reduce technical debt in Cashtab. This is step 1 of a series of diffs to combine `<BalanceHeader>`, `<BalanceHeaderFiat>`, `<ZeroBalanceHeader>` components into one standardized component that also shows distinction between spendable balance and total balance.
Looking to replace `getWalletBalanceFromUtxos` function from `cashMethods`. However, a number of new functions and refactors need to happen to achieve this goal.
Also, looking to get rid of the "everything is in the utils" folder pattern in Cashtab. `utils-v2` is a dumb name, but it is easy way for me to keep track of ongoing refactors while keeping diffs small.
When this refactor is complete, the exiting `utils` folder will be empty, and `utils-v2` will become just `utils`.