[herald] Improve getCoingeckoPrices to return tickers and ecash price first

Summary:
T2972

Depends on D13640

Improve getCoingeckoPrices function to return ticker info of cryptos (required in tg msg). Make sure ecash price is returned first (helpful for making tg msgs). Add unit test.

Test Plan:
Review changes to config and getCoingeckoPrices
npm test
npm run getCoingeckoPrices

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13641