GetRoutingRules client added

What's Changed

• Add Vtctld.GetRoutingRules client by @maxenglander in https://github.com/planetscale/planetscale-go/pull/313

New Contributors

• @maxenglander made their first contribution in https://github.com/planetscale/planetscale-go/pull/313

Full Changelog: https://github.com/planetscale/planetscale-go/compare/v0.168.0...v0.168.1