[Cashtab] [Cashtab] [final bch-api deprecation p4] Refactor tryNextApi function to try next chronik instance

Summary:
T2730, T2735

Depends on D12789

Refactor the tryNextAPI function to try the next chronik client instead of the next bch-api instance

Test Plan:
npm start
Wait for API error to display on home screen from bad chronik client URL
Note that API error automatically clears and app works
In dev log, note persistent attempts to reconnect to the bad websocket. This will be corrected in the next diff on this stack

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D12791