Clarify path param naming (#32969)

In history (from some legacy frameworks), both `:name` and `name` are
supported as path path name, `:name` is an alias to `name`.

To make code consistent, now we should only use `name` but not `:name`.

Also added panic check in related functions to make sure the name won't
be abused in case some downstreams still use them.

routers/api/v1/admin/cron.go

@@ -74,7 +74,7 @@ func PostCronTask(ctx *context.APIContext) {
 	//     "$ref": "#/responses/empty"
 	//   "404":
 	//     "$ref": "#/responses/notFound"
-	task := cron.GetTask(ctx.PathParam(":task"))
+	task := cron.GetTask(ctx.PathParam("task"))
 	if task == nil {
 		ctx.NotFound()
 		return