[cashtab] Move the chronik urls config out of Ticker.js

Summary:
The Ticker.js file is a big ball of mud that contains every config items including (and especially) the ones that are unrelated to tickers.

This diffs only move the chronik urls config out of this mess, but more similar extractions needs to happen.

Test Plan:

npm test # With this patch it fails on my machine the same way that it fails on master

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman, emack

Differential Revision: https://reviews.bitcoinabc.org/D14102