Top() function returns incorrect set of series

[alexanderzobnin]

Describe the bug
top() function returns wrong set of series.

Screenshots
Original set:

Returned by top(5, max):

Software versions

Grafana	Zabbix	Grafana-Zabbix Plugin
x.x.x	x.x.x	4.2.3

[alexanderzobnin]

This bug happens because of wrong custom sorting implementation here:
https://github.com/alexanderzobnin/grafana-zabbix/blob/750292296c1fcff7082b09747614fe66b3077961/pkg/timeseries/sort.go#L16-L19

In this case another slice (aggregatedSeries) is using for comparing values, but the Swap() function changes the original series slice, so algorithm does not work as expected. So the solution is either use series in comparison or fully implement sort interface (Len/Less/Swap methods).