chore(auth): Fix problem of global signout tests causing failures in other tests

[mattcreaser]

• PR title and description conform to Pull Request guidelines.

Issue #, if available:

Description of changes:
The global signout tests could cause failures when running tests on multiple devices concurrently. This is because the tests used the single shared user, which could sign out the shared user while it was in the middle of being used in a test on another device.

Updated to user the temporary user that is unique to that test run instead.

Also fixed issue where temporary users were not always being deleted.

How did you test these changes?
(Please add a line here how the changes were tested)

Documentation update required?

• No
• Yes (Please include a PR link for the documentation update)

General Checklist

• Added Unit Tests
• Added Integration Tests
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Ensure commit message has the appropriate scope (e.g fix(storage): message, feat(auth): message, chore(all): message)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.32%. Comparing base (cade307) to head (c88a350).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3144   +/-   ##
=======================================
  Coverage   54.31%   54.32%           
=======================================
  Files        1041     1041           
  Lines       31926    31926           
  Branches     4708     4708           
=======================================
+ Hits        17341    17344    +3     
+ Misses      12747    12745    -2     
+ Partials     1838     1837    -1     

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