feat(grafana-cli): allow configuring admin ID for reset-admin-password (#60603)

* feat(grafana-cli): add a flag to control the admin user's ID for reset-admin-password

Since this is now more permissive, I've also added validation that the requested user is an admin.

* slight refactor to support testing

pkg/cmd/grafana-cli/commands/commands.go

@@ -160,6 +160,11 @@ var adminCommands = []*cli.Command{
 				Usage: "Read the password from stdin",
 				Value: false,
 			},
+			&cli.IntFlag{
+				Name:  "user-id",
+				Usage: "The admin user's ID",
+				Value: DefaultAdminUserId,
+			},
 		},
 	},
 	{