Verify namespace proofs can be obtained in E2E tests

Currently on main we don't get namespace proofs for blocks > 1 in the native demo. Not yet sure since when that's the case but it should be relatively simple to add checks to the E2E tests to verify that we can obtain namespace proofs to avoid breakage in the future.

Start with the native demo's E2E tests and identify where blocks are produced and proofs are requested. Add checks covering blocks greater than 1, and consider the work done when the tests successfully obtain namespace proofs for those blocks.

Written by the indexing model from the issue text.