`maxVideoDuration` was added to the platform interface a long time ago
in preparation for adding that feature, but the other parts were never
landed. The previous state was:
- It has never been implemented for iOS or Android
- It has never been settable from the app-facing package, so is always
  null unless someone uses the platform interface directly, which we
  don't consider a supported use case.
- It cannot be implemented in the CameraX Android implementation.
- It was implemented for Windows and web because when those platforms
  were added much later, nobody realized that the parameter was unused.

There is no compelling need for this feature, as clients of the plugin
can simply set their own timer to stop recording. Given that, rather
than leave the confusing partial state, this marks the option as
deprecated at the platform interface layer and warns implementers that
it can be ignored. It also removes the implementations from Windows and
web in order to reduce implementation complexity, since that code was
not reachable from the app-facing API.

This does not consider the Windows and web changes to be breaking, even
though they arguably could be, because we do not expect clients to be
calling platform interface methods directly.