misc: Write migration tool

[dariusc93]

Under the current implementation, migration would happen internally where possible, but this may add additional delay in initializing the backend especially if there is a large dataset or if we would begin to attempt to migrate messages and could fail without any fallback. Ideally, the migration itself should be set aside into its own tool to migrate between different dataset version so this tool could be used instead for migrating to a newer internal schema, which may be safer and easier than performing it internally