EVM Node: Print SQLite schemas

It can be difficult to keep track of the current SQLite tables, considering we only keep successive migration scripts. Arguably, it is possible to infer the current schemas by reading the SQLite statements in evm_store.ml.

We propose a more direct way, by introducing a new command debug print store schemas. This one is not intented for end-users, but rather as a development tool. We add a regression test which can be used to review the current schemas without having to remember the command.

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