Added hostname resolution

[lougovsk]

Currently one mqtt client requires an ip address. However, often we want to use hostname instead. This change should account for that

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[awawa-dev]

Hi
In the past, we had a lot of problems with similar approach, for example when HyperHDR was running in a virtual container and several subnets were available. Then during such address auto-detection we didn't always get the one on the same subnet as the target we were supposed to communicate with (for example: #580). Alternatively, would manually entering the host address in the MQTT configuration solve the problem?

[awawa-dev]

Nevermind, it's a target. Should work.