chore(auth): Move SignOut to usecase

[mattcreaser]

• PR title and description conform to Pull Request guidelines.

Issue #, if available:

Description of changes:
Moves the logic for signout and clearFederationToIdentityPool to usecase classes.
Adds additional unit test coverage for these flows.

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

❌ Patch coverage is 86.41975% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.68%. Comparing base (37568a3) to head (394f019).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3146      +/-   ##
==========================================
+ Coverage   54.54%   54.68%   +0.14%     
==========================================
  Files        1044     1046       +2     
  Lines       31259    31251       -8     
  Branches     4695     4690       -5     
==========================================
+ Hits        17050    17091      +41     
+ Misses      12375    12332      -43     
+ Partials     1834     1828       -6     

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