Improve handling of obsolete migrations

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Now that we have an Advanced Search migration graveyard, we can remove really old deprecated migrations from the code base. Instead of relying on the Elastic::MigrationObsolete module, let's create a registry that can be used as a start-up check before running migrations. If a migration in the registry is obsolete and is about to be executed, the error in Elastic::MigrationObsolete should be raised and migration should be halted.

• A migration would always return true as completed if it is marked obsolete.
• If a migration is obsolete but is used in the code base, we should log a deprecation warning.
• A spec failure would need to be raised if a migration is in the registry but not in the filesystem.
• When a migration is removed from filesystem, we would remove from registry as well. An exception would be raised. (This code already exists in MigrationRecord.find_by_name!)

Have a YAML registry:

add_hidden_to_issues:
  obsolete: true
  marked_obsolete_in: "16.0"

Once the registry is in place, we can update the archive script to use it accordingly.