Improve module id errors

From a documentation issue:

"In the docs for modules (https://shiny.rstudio.com/py/docs/workflow-modules.html) it's not explicitly documented that the first argument for the id must be added silently. (Not sure I'm describing this correctly, or in the most elegant way.)

What I mean is that the function definition in the UI and server has one argument:

def counter_ui(label: str = "Increment counter"):
But when you call this function, you must prepend the ID, like this:

counter_ui("counter1", "Counter 1"),
So, when I say add the id silently, I refer to counter1 in this example. If you forget to do this, you get all kinds of very strange, non-descriptive errors."

I doubt we can solve this with documentation, so we should make the function error more gracefully.

Start with the workflow-modules documentation and the counter_ui and server function examples described in the issue. Reproduce a call that omits the required module ID, then trace the resulting error; done means the missing-ID case produces a clear, descriptive error instead of confusing failures.