Add option for preferred Sleep Proxy Servers

[awein]

Networks with multiple Apple TVs and HomePods will have several many Sleep Proxy Servers too choose from.

Unfortunately, all of those use the same set of properties (70-35-60-63.1) which does not allow for any kind of prioritization of one or the other. There is also no indication around the reliability of the devices network connectivity (WiFi / wired connection).

It would be useful to be able to manually specify which Sleep Proxy should be prioritized to work around this.