Golangci lint fixes (#195)

* Add golangci-lin as make target
* Fix: could omit type ... from declaration; it will be inferred from the right-hand side (staticcheck)
* Fix func intArrayContains is unused (unused)
* Fix: could use strings.ReplaceAll instead (staticcheck)
* Fix: could expand call to math.Pow (staticcheck)
* Fix: could use tagged switch on `...` (staticcheck)
* Fix: Error return value of `...` is not checked (errcheck)
* Fix: ineffectual assignment to err (ineffassign)
* Fix: There is no need to wait for command completion
* Add cpustat, diskstat and schedstat config
* Use slices to exclude metrics
* Replaced stringArrayContains by slices.Contains
* Replace m[k]=v loop with maps.Copy
* Use module slices from the standard library. Remove use of golang.org/x/exp/slices
* Use SplitSeq and max to modernize code

internal/metricAggregator/metricAggregator.go

@@ -10,6 +10,7 @@ package metricAggregator
 import (
 	"context"
 	"fmt"
+	"maps"
 	"math"
 	"os"
 	"strings"
@@ -121,9 +122,7 @@ func (c *metricAggregator) Init(output chan lp.CCMessage) error {
 
 func (c *metricAggregator) Eval(starttime time.Time, endtime time.Time, metrics []lp.CCMessage) {
 	vars := make(map[string]interface{})
-	for k, v := range c.constants {
-		vars[k] = v
-	}
+	maps.Copy(vars, c.constants)
 	vars["starttime"] = starttime
 	vars["endtime"] = endtime
 	for _, f := range c.functions {