refactor(storage): gaxios migration system test fix

[thiyaguk09]

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Fixes #<issue_number_goes_here> 🦕

[gemini-code-assist]

Code Review

This pull request updates the Google Cloud Storage client to use the /storage/v1 prefix for API endpoints and ensures Content-Type: application/json headers are explicitly set for POST requests. It also includes significant updates to system tests, such as skipping problematic public access tests, improving error handling in cleanup routines, and ensuring Node 18 compatibility in the transport layer. Review feedback identified a potential TypeError in getServiceAccount due to missing optional chaining, a bug in a test timeout callback that would cause tests to hang, and a potential type mismatch in error status assertions within the system tests.

[thiyaguk09]

/gemini_review