fix(Storage) Use default URLSession configuration for non-multipart uploads #1542

[jcjimenez]

Issue #, if available:
#1542

Description of changes:
This change maintains the use of the background URLSessionConfiguration + URLSession for upload operations that result in multi-part uploads and download operations but switches to a default URLSessionConfiguration for upload operations of smaller files that result in non-multipart uploads.

Check points: (check or cross out if not relevant)

• [x ] 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
• If breaking change, documentation/changelog update with migration instructions

DataStore checkpoints (check when completed)

• Ran AWSDataStorePluginIntegrationTests
• Ran AWSDataStorePluginV2Tests
• Ran AWSDataStorePluginMultiAuthTests
• Ran AWSDataStorePluginCPKTests
• Ran AWSDataStorePluginAuthCognitoTests
• Ran AWSDataStorePluginAuthIAMTests

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