Brokers status deadLetterUri is not been updated

[gabo1208]

Problem
Brokers and Triggers have the same status property: status.deadLetterSinkUri

In Trigger's Spec is clear how it should behave and when to update it. In the Broker's spec is not even mentioned.
I think we should decide between:

• Removing status.deadLetterSinkUri from the Broker's status (don't know if that is a good decision, if anyone can give a little bit more context about this it'll be helpful :))
• Fixing Brokers status behavior to update the status.deadLetterSinkUri when its appropriate and to add this behavior to the Broker's spec so its clear for everyone and consistent with other specs (like Subscriptions and Triggers)

Persona:
All

Exit Criteria
Reach a decision between both options for the status.deadLetterSinkUri and implement it.

Additional context (optional)
Add any other context about the feature request here.

[gabo1208]

As commented here, we are going to fix the brokers spec and code to make a MUST resolving the DLQ ref and updating the status.deadLetterSinUri with the resolved URI in the process.

[benmoss]

/assign @gabo1208