DAL/Node: add published_level to skip_list_slots table and migrate db

What

Migrate the DAL node's skip-list DB by adding a published_level column in the skip_list_slots table (and replacing attested_level by attestation_lag).

Two additional commits (the last two) are to ensure the right parameters are used around migration. See commit messages for details.

Why

A slot id identifies a slot. Therefore a skip-list cell should rather be identified (and indexed) by a slot_id = (published_level, slot_index) pair, and not by an (attested_level, slot_index) pair.

In particular, in a future planned protocol migration slots from several published levels will be attested at the same level. The current table is not able to distinguish them.

How

Just use the already provided DB migration mechanism.

Manually testing the MR

One could test it for instance on Shadownet (but any other testnet with a running producer is fine), eg slot index 8 on Shadownet:

• Start an operator node running on master following a slot index for which there is a producer.
• Run sqlite3 <path_to_dal_node_data_dir>/store/skip_list_store/store.sqlite
  • Run .headers on to see the column names.
  • Then run SELECT *, hex(skip_list_cell_hash) FROM skip_list_slots ORDER BY attested_level DESC LIMIT 32;
• Stop the DAL node, and restart it on the current branch (but the same data-dir).
• Run the same sqlite3 command.
  • Run SELECT *, hex(skip_list_cell_hash) FROM skip_list_slots WHERE published_level = <attested_level_from_above> - 8. You should now see the same data and with an additional 1st column (published_level).