EW: Prompt users to turn on key storage (on a verified device)

[mxandreas]

Problem

The key storage has not been turned ON automatically for EW users (e.g. at account creation) and even this would change, there would be a lot of accounts which does not have it ON. Yet, this is a pre-requisite for setting up recovery which we want to highly recommend.

Design

• The goal is to prompt the user to turn on key storage via a toast.
• This toast should be displayed whenever key storage is OFF & the user has not dismissed the toast previously:
  • The user can dismiss the toast (for good) as indicated in the designs.