Switch: check switch status

### Description

It would be great if the switch node could report its current state by receiving a “check” message. The output message would include an input field containing the value of the incoming payload. This would make it possible to determine why the output message was emitted (locally or due to some input value).

This would enable things like checklists, master switches, and similar logic on dashboards without any custom programming by chaining switches together. The same functionality can currently be achieved by storing the switch value in the flow context and reading it elsewhere, but this feature would remove a lot of unnecessary programming.

Here is an examples of what the flow could look like if such a feature existed.

### Have you provided an initial effort estimate for this issue?

I am no FlowFuse team member