Add label/icon for different AI Catalog item types

We now have a few AI Catalog item types that will be displayed in the same lists:

• Agents: Includes AGENT and (maybe?) FOUNDATIONAL_AGENT.
• Flows: Includes FLOW and THIRD_PARTY_FLOW.

We need some sort of label/icon, possibly with a tooltip that shows in the following pages:

• Listing page.
• Show page.

This might be related to work done in #573263.