[native] Show alert when login fails due to outdated client version

Summary: This diff addresses the "easy part" of ENG-8113.

Test Plan:
There are a lot of spots here, and I didn't check all of them. I verified the core parts:

1. That identity service returns Unsupported version and keyserver returns client_version_unsupported when the client version is outdated
2. That the Alerts showed correctly
3. That goBackToPrompt worked

Reviewers: inka

Reviewed By: inka

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D12082