Create Knative CRD Icons for use in diagrams and UI

It would be great to have official icons for each Knative CRD (Service, Revision, Channels, Brokers, etc.) so that they can be used in service architecture diagrams and UIs to represent Knative resources.

Creating this issue in community as:
1. Icons seem like "community material"
2. Likely needs Steering Committee support as it relates to the Knative brand

cc @bbrowning @mattmoor

Start by reviewing this issue and the referenced Knative CRD examples, including Service, Revision, Channels, and Brokers. Seek Steering Committee guidance on branding and scope before proceeding. Done means an agreed official icon set exists for the identified Knative resources and is suitable for architecture diagrams and UIs.

Written by the indexing model from the issue text.