refactor(tests): Extract tests related logic into raw::tests for reuse

[Xuanwo]

This extract tests related logci into raw::tests for better reusing. raw::tests is hiden under tests features that users won't touch that unexpected.

This change makes it much easier to reproduce our fuzzing tests:

pub async fn test_fuzz_issue_2717(op: Operator) -> Result<()> {
    let actions = [ReadAction::Seek(SeekFrom::End(-2))];

    test_fuzz_read(op, 2, .., &actions).await
}

[suyanhanx]

Thanks!