[ecash-price] Add more fiat

Summary: And and a facility to list them all. This can be used to build a list of supported currencies.

Test Plan:

pnpm test

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D19344