[Cashtab] Prevent token qty errors on listings for large quantities

Summary:
Do all the math in Orderbook with BigInt and token satoshis. Do all the rendering with decimalized quantities.

This resolves errors caused by step calculations for large token quantitites with large decimals getting off because JS numbers.

Test Plan: npm test

Reviewers: #bitcoin_abc, Kronkmeister

Reviewed By: #bitcoin_abc, Kronkmeister

Differential Revision: https://reviews.bitcoinabc.org/D17008