[Cashtab] Move the websocket config out of Ticker.js

Summary: Similar to D14102, this diff moves the websocket specific urls out of Ticker.js and into its own config.

Test Plan:

• grep -r config.websocketDisconnectedRefreshInterval src/ and ensure no results
• grep -r config.websocketConnectedRefreshInterval src/ and ensure no results
• npm test
• npm start and observe successful wallet refresh intervals
• send XEC tx and ensure successful broadcast
• receive XEC tx and ensure successful websocket detection

Reviewers: bytesofman, #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14110