* clean up intervalv2 functions
* use roundInterval from grafana-plugin-sdk-go
* use from grafana-plugin-sdk-go
* have intervalv2 in publicdashboards and remove tsdb/intervalv2
* legacydata cleanup
* remove unused variables
* Update pkg/tsdb/legacydata/interval/interval.go
Co-authored-by: Arati R. <33031346+suntala@users.noreply.github.com>
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Co-authored-by: Arati R. <33031346+suntala@users.noreply.github.com>