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/buildinternalplugins.go

@@ -17,7 +17,7 @@ func BuildInternalPlugins(c *cli.Context) error {
 	}
 
 	const grafanaDir = "."
-	metadata, err := GenerateMetadata(c)
+	metadata, err := config.GenerateMetadata(c)
 	if err != nil {
 		return err
 	}