test(storage/driver): add integration tests for internal presigned URLs expiry option

Related to #406.

This is in preparation for adding a new externally exposed expiry delay option to allow customizing the longevity of presigned URLs for storage backends that support it.

This MR adds integration tests for this particular area of the code (the internal expiry option which is not exposed to the outside) which had none so far. A few optimizations were done in order to allow tests to pass but no functionality has changed.

This has been manually tested against GCS, OSS, and Azure (not fun 🙂). S3 and Swift are covered by the existing CI tests.