feat: Avoid throwing errors for shared input/output IDs (#4101)

* refactor: Factor out message display from error handler

* feat: Add custom event for sending a client message

* feat: Report binding validity problem via event instead of throwing error

* feat: Don't need to hide shared input/output message

Now that it's not an error, it's safe to report

* refactor: Move `inDevMode()` logic into error console

* refactor: Rename `.error` --> `.event`

* feat: wrap client error message

It's otherwise hard to tell that the error is scrollable
Plus the scrolling is over the whole message rather than the part that overflows

* feat: always send client console messages to browser console as well

* chore: throw if `shiny:client-message` receives an event that isn't CustomEvent

* feat: Handle status in `showShinyClientMessage()`

* Renamed `showMessageInClientConsole()` to `showShinyClientMessage()` to improve clarity

* Added `status` argument to `showShinyClientMessage()` to allow for different message types

* refactor: Don't throw errors for duplicate IDs

Brings dev mode in line with current "prod" behavior,
where errors aren't thrown for duplciates. In both cases
we still get console or client messages.

* refactor: Clean up `status` inside `checkValidity()`

* refactor: Have `checkValidity()` handle emitting the client console event

NEWS.md

@@ -22,6 +22,8 @@
 
 * Fixed a bug with stack trace capturing that caused reactives with very long async promise chains (hundreds/thousands of steps) to become extremely slow. Chains this long are unlikely to be written by hand, but {coro} async generators and {elmer} async streaming were easily creating problematically long chains. (#4155)
 
+* Duplicate input and output IDs -- e.g. using `"debug"` for two inputs or two outputs -- or shared IDs -- e.g. using `"debug"` as the `inputID` for an input and an output -- now result in a console warning message, but not an error. When `devmode()` is enabled, an informative message is shown in the Shiny Client Console. We recommend all Shiny devs enable `devmode()` when developing Shiny apps locally. (#4101)
+
 * Updating the choices of a `selectizeInput()` via `updateSelectizeInput()` with `server = TRUE` no longer retains the selected choice as a deselected option if the current value is not part of the new choices. (@dvg-p4 #4142)
 
 # shiny 1.9.1