Test for blockage migration from both levels 3 and 4

This adds a test to verify that the user can perform the blockage migration protocol when their credential's level is 4.

Specifically, in this test, the user's level now goes 0 -> 1 - > 2 - > 3 -> 4 -> 2 (blockage migration) -> 3 -> 1 (blockage migration).

Blockage migration is only allowed when the user's level is 3 or 4, so the test now checks both cases.