fix(predictions): use serial queue for WebSocketSession delegate queue

[thisisabhash]

Issue #

Customers have reported receiving intermittent InvalidSignatureException during liveness checks.

Description

According to Apple docs, URLSession delegate queue should use a serial queue for delegate and completion handler callbacks. This PR updates the URLSession initializer with a serial queue.
Also, calls to WebSocketSession object APIs are put under a serial queue as well.

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

Attention: Patch coverage is 0% with 14 lines in your changes missing coverage. Please review.

Project coverage is 67.75%. Comparing base (abd17e5) to head (57b2fe4).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...sPlugin/Liveness/Service/FaceLivenessSession.swift	0.00%	8 Missing ⚠️
...ionsPlugin/Liveness/Service/WebSocketSession.swift	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3935      +/-   ##
==========================================
- Coverage   67.76%   67.75%   -0.02%     
==========================================
  Files        1125     1125              
  Lines       52117    52126       +9     
==========================================
  Hits        35316    35316              
- Misses      16801    16810       +9     

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	73.65% <ø> (+0.01%)	⬆️
DataStore_plugin_unit_test	83.36% <ø> (-0.06%)	⬇️
Geo_plugin_unit_test	74.86% <ø> (ø)
Logging_plugin_unit_test	63.11% <ø> (ø)
Predictions_plugin_unit_test	35.42% <0.00%> (-0.08%)	⬇️
PushNotifications_plugin_unit_test	88.43% <ø> (ø)
Storage_plugin_unit_test	76.92% <ø> (+0.04%)	⬆️
unit_tests	67.75% <0.00%> (-0.02%)	⬇️

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