Move Duo Workflow into the same sidebar view as Agentic Chat

Problem

Duo Workflow (now called Agent Platform) and its software development Flow currently use a completely separate icon in the editor's sidebar. This is highly confusing to users as it becomes hard to know which to use and why there are multiple sidebar icons for GitLab's Duo features.

Additionally it requires separate work to make both Agentic Chat and Workflow/Agent Platform available across IDEs, having both in a single view should make that easier.

Desired Outcome

We create a two tabbed interface to allow rendering both Chat and Agent Platform to render in the same sidebar.

Example with old naming: