Function to return first or last migration for arches version

[jacobtylerwalls]

When writing a migration in an arches applications, it is necessary to specify a lower bound for the dependency on the core arches migrations, and sometimes even an upper bound (via run_before) if there were breaking changes in core.

Rather than hunting for this information by checking the git history, it would be more convenient to be able to do:

    dependencies = [
        last_migration_for_arches_version("7.6"),
    ]
    run_before = [
        first_migration_for_arches_version("8.0"),
    ]