Add super_sliver_list.test

[knopp]

super_sliver_list is an alternative to SliverList (and ListView) with different performance characteristics and ability to reliably jump / animate to any item.

It relies heavily on scrollOffsetCorrection in a way no other sliver in Flutter does and thus may be somewhat prone to breaking (for example it was broken in past by https://github.com/flutter/flutter/pull/107735, which was reverted later).

Pre-launch Checklist

• [x] I read the Contributor Guide and followed the process outlined there for submitting PRs.
• [x] I read the Tree Hygiene wiki page, which explains my responsibilities.
• [x] I read the Flutter Style Guide recently, and have followed its advice.
• [x] I signed the CLA.
• [x] I listed at least one issue that this PR fixes in the description above.
• [x] I updated/added relevant documentation (doc comments with ///).
• [x] I added new tests to check the change I am making, or this PR is test-exempt.
• [x] All existing and new tests are passing.

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