Add support for `@MessageHandlerInterceptor`

[smcvb]

Feature Description

Provide, for example, gutter icons for the @MessageHandlerInterceptor.
This currently is provided for the @CommandHandlerInterceptor.
I'd assume implementing a similar level of support for the more generic @MessageHandlerInterceptor wouldn't prove too difficult.

Current Behaviour

There is no support for the @MessageHandlerInterceptor.

Wanted Behaviour

That there's support for the @MessageHandlerInterceptor.

Possible Workarounds

None that I know off.