This PR swaps out the custom pathway to publishing and rendering mention warnings after a message is sent.
ChatPublisher#publish_notice is used, and expanded. Now, instead of only accepting text_content as an argument, component and component_args are accepted and there is a renderer for these components.
Translations moved to server, as notices expect text to be passed in unless a component is rendered
The warnings are rendered at the top now, outside of the scope of the single message that sent it.
I entirely removed the jit_messages_spec b/c it's duplicate testing of other parts of the app. IMO we don't need a backend test for a feature, a component test for the feature AND a system test (that is slow and potentially even flakey due to timing issues with wait) to test the same thing. So jit_messages_spec is gone.
