Parallelise object storage packages scenarios

What does this MR do and why?

Parallelises object storage scenarios that run multiple package tests.

These tests are very verbose and consume a lot of logging, causing

Job's log exceeded limit of 4194304 bytes.
Job execution will continue but no more output will be collected.

when there are failures (due to retries). Related: https://gitlab.com/gitlab-org/gitlab/-/issues/359983.

MR acceptance checklist

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