chore: Improving WebAuthn integ tests

[ruisebas]

Description

This PR makes some changes to reduce the "flakyness" of the WebAuthn integration tests, and to provide better error messages.

General Checklist

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• All integration tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• New or updated tests include Given When Then inline code documentation and are named accordingly testThing_condition_expectation()
• If breaking change, documentation/changelog update with migration instructions

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 67.75%. Comparing base (9940908) to head (0472fcd).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3940      +/-   ##
==========================================
- Coverage   67.77%   67.75%   -0.03%     
==========================================
  Files        1125     1125              
  Lines       52117    52117              
==========================================
- Hits        35321    35310      -11     
- Misses      16796    16807      +11     

Flag	Coverage Δ
API_plugin_unit_test	70.33% <ø> (ø)
AWSPluginsCore	70.36% <ø> (ø)
Amplify	47.89% <ø> (ø)
Analytics_plugin_unit_test	85.20% <ø> (ø)
Auth_plugin_unit_test	73.66% <ø> (-0.04%)	⬇️
DataStore_plugin_unit_test	83.30% <ø> (-0.07%)	⬇️
Geo_plugin_unit_test	74.86% <ø> (ø)
Logging_plugin_unit_test	63.11% <ø> (ø)
Predictions_plugin_unit_test	35.49% <ø> (ø)
PushNotifications_plugin_unit_test	88.43% <ø> (ø)
Storage_plugin_unit_test	76.88% <ø> (ø)
unit_tests	67.75% <ø> (-0.03%)	⬇️

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