fix(Storage): Removing testable import on PresignURL extension

[ruisebas]

Issue #

• module 'AWSS3' was not compiled for testing #3877

Description

Removing the testable annotation when importing AWSS3 which was added because some types became internal. Instead, I'm replicating the types locally.

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
  • https://github.com/aws-amplify/amplify-swift/actions/runs/10945539621
• 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 51 lines in your changes missing coverage. Please review.

Project coverage is 68.20%. Comparing base (1ec20d0) to head (5fbfd6a).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...Plugin/Dependency/UploadPartInput+presignURL.swift	0.00%	51 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3878      +/-   ##
==========================================
+ Coverage   68.14%   68.20%   +0.06%     
==========================================
  Files        1085     1085              
  Lines       37992    38040      +48     
==========================================
+ Hits        25889    25945      +56     
+ Misses      12103    12095       -8     

Flag	Coverage Δ
API_plugin_unit_test	69.32% <ø> (ø)
AWSPluginsCore	68.53% <ø> (ø)
Amplify	47.12% <ø> (+0.01%)	⬆️
Analytics_plugin_unit_test	84.52% <ø> (ø)
Auth_plugin_unit_test	79.30% <ø> (-0.09%)	⬇️
DataStore_plugin_unit_test	82.17% <ø> (+0.94%)	⬆️
Geo_plugin_unit_test	72.06% <ø> (ø)
Logging_plugin_unit_test	62.99% <ø> (ø)
Predictions_plugin_unit_test	35.94% <ø> (ø)
PushNotifications_plugin_unit_test	86.21% <ø> (ø)
Storage_plugin_unit_test	75.46% <0.00%> (-1.03%)	⬇️
unit_tests	68.20% <0.00%> (+0.06%)	⬆️

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