Allow creating Event Source for an existing Channel

Description

As a user,

I want to be able to create a Knative Event Source for the previously created Knative Eventing Channel. This should be achieved by dragging the blue arrow that appears when moving the cursor over the Channel. This option is already available for Knative Services as "Event Source". The Channel can be bound to an Event Source as well so the same option should be added to the Channel alongside the "Add Subscription" option (attaching a screenshot).

Acceptance Criteria

1. Both Subscription and Event Source can be created for a Channel when a cursor is moved over the Channel and the blue arrow is clicked.

Additional Details: