[Cashtab] Make listing amounts more readable in agora listing notifications

Summary:
We want to make sure all rendered decimalized token quantities are in locale format, as it is otherwise very difficult to read the value

Have noticed these in normal app use

Test Plan:
npm test

List an amount of some token greater than 1000

Confirm there is a locale thousands separator, i.e. "1,000" in the notification amount

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D17592