Metadata: Move and rename genversions.go and genversions_test.go (#60315)

* Move and rename genversions.go and tests

* Fix lint - bring back cli.Exit

* Move package.json and fix tests

* Add necessary env vars for promote event

pkg/build/cmd/buildfrontend.go

@@ -3,6 +3,7 @@ package main
 import (
 	"log"
 
+	"github.com/grafana/grafana/pkg/build/config"
 	"github.com/grafana/grafana/pkg/build/errutil"
 	"github.com/grafana/grafana/pkg/build/frontend"
 	"github.com/grafana/grafana/pkg/build/syncutil"
@@ -10,7 +11,7 @@ import (
 )
 
 func BuildFrontend(c *cli.Context) error {
-	metadata, err := GenerateMetadata(c)
+	metadata, err := config.GenerateMetadata(c)
 	if err != nil {
 		return err
 	}