[native][web] Stop clearing user input on unknown error

Summary: The users info is almost always correct in the case of an unknown error, so we shouldn't clear it. Had this thought while investigating ENG-8727, which I realized would have never occurred for me if we didn't do this.

Test Plan:

1. I tested the native login workflow by killing the keyserver and confirming that the user input wasn't cleared after I got the Unknown error alert
2. To test the native legacy registration workflow while usingCSAT=true I had to hardcode the value of initialNotificationsEncryptedMessage. Otherwise did the same (kill keyserver and test)
3. I skipped testing web since the changes were so minimal and killing the keyserver means I can't load it, so the testing would be slightly harder

Reviewers: tomek, inka

Reviewed By: tomek

Differential Revision: https://phab.comm.dev/D12682