[Cashtab] Move seed phrase to dedicated wallet backup screen
Summary:
T2207
It's not intuitive that this is on the Settings screen. Move to its own component.
Add an alert in Settings in case a user is looking for it there.
Test Plan:
npm test
user browser is not in english:
user browser is in english:
Reviewers: #bitcoin_abc, emack
Reviewed By: #bitcoin_abc, emack
Differential Revision: https://reviews.bitcoinabc.org/D15867