[accounts] Merging of duplicates

[seland]

Feature / Issue

As a user I'm confused by having two separated accounts with the same keys (private, identity, wallet, etc). This happens because we didn't handle that case when recovering account.

Todos

• [ ] Change a way of recovering so that the same account won't be created (instead will be logged in into existing one).
• [ ] Create UI design for choosing which account from duplicates should be kept (@mimetic)
• [ ] Implement UI and logic on Pangea.

Acceptance criteria

• [ ] Duplicated user accounts are removed

Additional information

It may be thought together with #480.

[hunght]

this will be done on Friday 24 August