[e.cash] Update live transaction times in realtime

Summary: Currently the time-since value on the transactions is static. Adding an interval to update the times every 5s so the values stay more accurate.

Test Plan: preview and check

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman, Mengerian

Differential Revision: https://reviews.bitcoinabc.org/D19355