ARM64 Support

Hetzner Cloud released ARM64 servers, we have to check whether everything is supported and add missing functionality to hcloud-ruby.

• Server Types support a filter architecture in queries (Docs)
• Server Types have a new attribute architecture (Docs)
• Images support a filter architecture in queries (Docs)
• Images might also have an attribute architecture? Could not find it in the API Docs, though
• ISOs have two new filters architecture and include_architecture_wildcard (Docs)
• ISOs have a new attribute architecture (Docs)