Don't use `msg_clear` to determine message state

[folke]

Currently, message state is maintained by relying on Neovim message state (msg_clear).

It would be better to handle this by Noice using configurable timeouts.

This would make some of the code easier to work with and would fix some issues with messgages expiring before they have been displayed. (this can happen in async contexts like timers)

TODO

• [ ] View.dispatcher boolean to determine if the view is dispatching messages (like Notify, and Mini) and as such is not interested in the active messages state, or shows a view of the current state.
• [ ] for non dispatchers, timeout should clear messages in a View, once new non-cleared messages come in