CI: move grabpl package command to pkg/build (#55651)

* add grabpl package

* update .drone.yml

* resolve lint errors

pkg/build/cmd/main.go

@@ -124,6 +124,19 @@ func main() {
 			Usage:  "Exports version in dist/grafana.version",
 			Action: ExportVersion,
 		},
+		{
+			Name:      "package",
+			Usage:     "Package one or more Grafana variants",
+			ArgsUsage: "[version]",
+			Action:    ArgCountWrapper(1, Package),
+			Flags: []cli.Flag{
+				&jobsFlag,
+				&variantsFlag,
+				&editionFlag,
+				&buildIDFlag,
+				&signFlag,
+			},
+		},
 		{
 			Name:   "store-storybook",
 			Usage:  "Integrity check for storybook build",