Local (client) scope for dashboard nodes

### Description

Dashboard nodes can be instantiated across multiple concurrent dashboard clients, but maintain a single state/value (replicated automatically across clients). In multi-user scenarios, there is a need for local client scope (for example: per-client input fields & progress indicators).
It is possible to provide this multi-user functionality by programming around the nodes (filtering messages based on client id), yet it would be beneficial to enable this as a built-in capability.
The proposed feature is to add a checkbox to all dashboard nodes (or at least to **ui-template**), indicating the scope. If checked, incoming messages will be tested for a client-id property, and will accept the message only if either:
- The client id is matches the current client, or
- The message has is no client id property

The flow will be able to dynamically set the message scope, by adding/deleting the client id property.

**Note**: the client id can be the existing **socketid** property, or a new dedicated id. It is assumed that all outgoing messages from dashboard nodes automatically include this id (as done today).

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

I have provided an initial effort estimate