EagleIO poller creating dup messages

The EagleIO poller is using a message hash to try and avoid dup messages but it doesn't seem to be working.

See logical device 283 for example. Some data points are being recorded many times, with a timestamp from 2022.

Perhaps the hash calculation is using too much info so something is changing the hash when the data points themselves are not changing.

I now see some of the values are changing, eg salinity & temperature are not getting value-specific timestamps, but these ones that are not changing such as battV, adc ch3, etc keep getting added to the message even though their timestamps and values are not changing.

That explains why the hash keeps changing, and it would do so even if only calculated using the timeseries array.

We should talk about this and see whether those old values can or should be filtered out.