HttpTrigger with empty methods does not to respond to all methods

Based on the [HttpTrigger docs](https://docs.microsoft.com/en-us/azure/azure-functions/functions-bindings-http-webhook#trigger---configuration), if the methods are left empty in the HttpTrigger definition, it should respond to all methods.

When not explicitly defined, the HttpTrigger annotation in Java generates an empty `methods` array in function.json. This means the function doesn't respond to any HTTP methods at all and is inconsistent with the docs and the way the trigger works in other languages.