Dal/Sc_rollup: remove risky code duplication

Context

The same check is implemented twice. It's risky to modify one and forget to do the same with the other. So, this MR, exposes the function in the protocol (SORU refutation in presence of DAL pages) and re-uses it in the rollup part to check which pages should be feeded to the kernel.

Fixes #6263 (closed)

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR