Util: Improve performance of strings.SplitString (#49115) (#49654)

Replaces the regexp with calls to strings.ReplaceAll and strings.Fields
for simplicity and improved performance.

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>
(cherry picked from commit 1f85101787)

Co-authored-by: Dave Henderson <dave.henderson@grafana.com>

pkg/util/strings.go

@@ -3,7 +3,6 @@ package util
 import (
 	"fmt"
 	"math"
-	"regexp"
 	"strings"
 	"time"
 	"unicode"
@@ -34,7 +33,7 @@ func SplitString(str string) []string {
 		return []string{}
 	}
 
-	return regexp.MustCompile("[, ]+").Split(str, -1)
+	return strings.Fields(strings.ReplaceAll(str, ",", " "))
 }
 
 // GetAgeString returns a string representing certain time from years to minutes.