[Cashtab] Pull to refresh updates wallet state instead of reloading the page

Summary:
The pure window reload does not work on the native app webview. The promise does not resolve and the user sees a spinner indefinitely.

Replace a page refresh with a wallet sync, which is the most commonly needed action.

There is room for improvement here as some pages may need special types of manual reloading. But these pages can be refreshed by navigation. A simple pull to refresh for wallet state fixes the existing bug and adds a useful feature.

Test Plan: npm test

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D19201