Set filename when the file is not stored locally

What does this MR do and why?

Set filename when the file is not stored locally.

Follow-up from: https://gitlab.com/gitlab-org/gitlab/-/issues/383060

Testing project (on staging): https://staging.gitlab.com/govern-team-test/yarn-remediation/-/dependencies

Code reference to the distinction between the different storages: https://gitlab.com/gitlab-org/gitlab/-/blob/c8a06a8918b5e09f91526bfbac953da999042d87/lib/api/helpers.rb#L609

Different behaviour across different environments:

Stored Locally:

[9] pry(main)> Dependencies::DependencyListExport.find(2).file.url
=> "/uploads/-/system/dependencies/dependency_list_export/file/2/root-vuln-test_dependencies_2023-01-04T1458.json"
[10] pry(main)> Dependencies::DependencyListExport.find(2).file.file_storage?
=> true

Not stored locally:

[ gstg ] production> Dependencies::DependencyListExport.last.file.url
=> "https://storage.googleapis.com/gitlab-gstg-uploads/dependencies/dependency_list_export/file/2/govern-team-test-yarn-remediation_dependencies_2023-01-04T1455.json?GoogleAccessId=gitlab-object-storage@gitlab-staging-1.iam.gserviceaccount.com&Signature=e7DriMuW8Gn0oW%2FHsCqjd%2BG8G97JuLYBloDcBZJ3zP9jMSMc1rn%2FUMKCfZpt%0AFTGHQV2hQ%2BYsDkZ0q3iMbO8%2BKSiABTjWdsXPUXl2Dhddc%2BhkVPn96OAapo2r%0AK89QdpJHgwG8NffjpR5lyB8LXXSjhCLbiSFv67bkFzMD5CJekaiNCZ5GsVGr%0AHPRkygom3K4xKY1EPTS1wWJRty4GrDoCnHC7vJhxtHgCwqrNVPZBXl%2BtXToB%0AN2ssJ%2Fu5jM6vz6FAZFvwn3WT2uysN7%2FcuxYOk7NwrX8jP3x0Y85dyuOOIhrB%0A%2FkIGOXMicyUUVb8TLsVyFWjyRZpi%2BHvK3w8%2FugRrYw%3D%3D&Expires=1672847989"
[ gstg ] production> Dependencies::DependencyListExport.last.file.file_storage?
=> false

Screenshots or screen recordings

Filename isn't set when file isn't stored locally.

How to set up and validate locally

Unfortunately the issue can't be reproduced via GDK. As this feature is still behind a feature flag (i.e., dependency_list_exporter), the issue is not present in production.

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.