[Cashtab] Update getSlpSendTargetOutputs to match optimizations of getSlpBurnTargetOutput

Summary:
Depends on D15100

• Fix typo in toLocaleString() implementation
• Use tokenUtxo.slpToken.amount which, in the chronik utxo object, is already undecimalized (so save the op)

Test Plan: npm test

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D15101