Loki: Implement step editor (#69648)

* Loki: Implement step editor

* Update to keep value

* Remove console.log

* Remove white space

* Update public/app/plugins/datasource/loki/querybuilder/components/LokiQueryBuilderOptions.tsx

Co-authored-by: Matias Chomicki <matyax@gmail.com>

* Import trim

* Update using of step in split queries

* Add tests

* Add tests

* Remove step interpolation

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Co-authored-by: Matias Chomicki <matyax@gmail.com>

pkg/tsdb/loki/parse_query.go

@@ -126,7 +126,10 @@ func parseQuery(queryContext *backend.QueryDataRequest) ([]*lokiQuery, error) {
 		interval := query.Interval
 		timeRange := query.TimeRange.To.Sub(query.TimeRange.From)
 
-		step := calculateStep(interval, timeRange, resolution)
+		step, err := calculateStep(interval, timeRange, resolution, model.Step)
+		if err != nil {
+			return nil, err
+		}
 
 		expr := interpolateVariables(model.Expr, interval, timeRange)