Add service account support for Google Cloud Storage client initialization

[dannon]

Can we squint at this and call it a bug so we can target to 25.1?

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[github-actions]

This PR was merged without a "kind/" label, please correct.